Sailing Glossary

Descriptions of marine terms.


Abaft: Behind, toward a vessel’s stern.
Abeam: Off the side, amidships, at right angles to the fore and aft line.
Abreast: Side by side; by the side of.
Adrift: Not made fast, floating loose, at mercy of wind and current.
Aft: At, near, or toward the stern.
Aground: Touching or stuck on the bottom.
Ahead: In front of the vessel, forward; opposite of astern.
Aids To Navigation: Artificial objects to supplement natural landmarks indicating safe and unsafe waters.
AIS: System where vessel information (location, course, speed, etc.) is broadcast by VHF radio, for use by other vessels in navigation and collision avoidance. See also article – How is AIS works
Alee: Away from the direction of the wind. Opposite of windward.
Aloft: Above deck, usually in the rigging.
Amidships: In or toward a boat’s middle part, between the sides or between bow and stern.
Anchorage: A place suitable for anchoring in relation to the wind, seas and bottom.
Apparent Wind: The speed and direction from which the wind appears to blow with reference to the bow when the boat is moving (also called relative wind).
Arrival Alarm: An alarm signal issued by a GPS/chart plotter that indicates arrival at or at a predetermined distance from a waypoint (see arrival circle).
Arrival Circle: An artificial boundary placed around the destination waypoint of the present navigation leg, the entering of which will signal an arrival alarm.
Astern: At any point behind the boat, backward.
Athwart: At right angles to the fore-and-aft line of a vessel.
Aweigh: The position of anchor as it is raised clear of the bottom.


Bathymetric Line: A depth contour line on the chart
Batten: Stiffening strip placed in leech of sail. Also, a wooden strip fastened over seam to stop leakage.
Batten Down: Secure hatches and loose objects both within the hull and on deck.
Beacon: A marked post located on a shoal or bank to warn vessels of danger or to mark a channel. A signal mark on land; a light or radio signal.
Beam: The greatest width of the boat.
Bear Off: Steer away from the wind, shore or any object.
Bearing: The direction of an object expressed either as a true bearing as shown on the chart, or as a bearing relative to the heading of the boat.
Bearing Away: Turning away from the wind.
Bilge: The lowest part of the ship’s interior.
Bitter End: The inboard (free) end of a line or rope.
Boom: A pole running at a right angle from the mast.
Boot Top: A painted line that indicates the designed waterline.
Brightwork: Varnished woodwork and/or polished metal.
Broach: The turning of a boat broadside to the wind or waves, subjecting it to possible capsizing.
Bulkhead: A vertical partition separating compartments.
Bulwark: Extension of topsides above deck.
Burdened Vessel: That vessel which, according to the applicable Navigation Rules, must give way to the privileged vessel. The term has been superseded by the term “give-way”.


Cast Off: To let go a line, as to cast off a bow line.
Chafing Gear: Tubing or cloth wrapping used to protect a line from chafing on a rough surface.
Chine: Intersection of sidesand bottom of a boat.
Chock: A deck fitting to guide aline where it leaves the boat. Also a wedge or bracket to keep articles from shifting.
Clear Astern And Clear Ahead: One yacht is clear astern of another when her hull and equipment in normal position are behind a line abeam from the aft most point of the other boat’s hull and equipment in normal position. The other yacht is clear ahead.
Cleat: A fitting to which lines are made fast. The classic cleat to which lines are belayed is approximately anvil-shaped.
Clew: Aft, lower corner of a sail.
Close Hauled: Sailing as directly into the wind as possible, also, on the wind.
Coaming: A vertical piece around the edge of a cockpit, hatch, etc. to prevent water on deck from running below.
Come About: Significant course change in sailing to bring the bow through the wind or tack.
Compass Error: Combined effect of variation and deviation.
Cpa – Closest Point Of Approach: The closest distance two vessels will come to each other based on their current course and speed.
Cunningham (Also Called A Downhaul): Adjusting the tension of a sail’s luff.


Dead Ahead: Directly ahead.
Dead Astern: Directly aft.
Deck: A permanent covering over a compartment, hull or any part thereof.
Deviation: Disturbing effect of boat’s magnetic field upon its compass.
DGPS: differential data is received from external DGPS Receiver
Displacement Hull: A type of hull that plows through the water, displacing a weight of water equal to its own weight, even when more power is added.
DNT: Distance to the next position the NX40/45 is navigating to, either a waypoint or the cursor.
Dock: A protected water area in which vessels are moored.The term is often used to denote a pier or a wharf.
Dolphin: A group of piles driven close together and bound with wire cables into a single structure.
Draft: The depth a vessel sinks when afloat, as measured vertically from the waterline to the lowest point.
Drogue: Object streamed from boat to decrease speed, sea anchor.


Ebb: A receding current.
EVC – Electronic Vessel Control: enables boat’s engine, transmission, instruments and control systems to communicate and exchange information via a common bus network. Through proper interface to EVC, an autopilot can get sensor data from the EVC, do steering calculations and send rudder commands back to the EVC which brings rudder to commanded angle.


Fairlead: Fitting to route control lines or cables.
Fathom: A unit of length used in measuring water depth.One fathom is 6 feet.
Feet Ft: 1 foot is 0.3048 meter
Fender: A cushion, placed between boats, or between a boat and a pier, to prevent damage.
Fish Forecaster: An estimate of the likelihood of catching fish based on barometric pressure. The more fishes that show the higher the likelihood (requires Simrad 721 VHF radio).
Fishfinder: A fish-finder is an echo sounder (sonar) specifically designed to detect the presence of fish in the underwater environs of the host boat, in addition to measuring the overall depth of the water. A fish-finder uses echo-location to reflect electronic pulses off fish and other underwater features and converts this information into a graphic rendition, nowadays a full-colour high-definition screen or liquid crystal display unit. The image on the screen, which represents individual fish with a small icon or as a series of arcs, enables fishermen to identify suitable targets and lower their baits or lures to the correct depth.
Flare: The outward curve of a vessel’s sides near the bow. A distress signal.
Flood: A incoming current.
Fluke: The palm of an anchor.
Following Sea: An overtaking sea that comes from astern.
Fore: Prefix denoting at, near, or towards the bow.
Fore-And-Aft: In a line parallel to the keel.
Forepeak: A compartment in the bow of a small boat.
Forward: Toward the bow of the boat.
Foul: Not clear, jammed.
Foul Ground: A place not suitable for anchoring.
Fouled: Any piece of equipment that is jammed or entangled, or dirtied.
Freeboard: The minimum vertical distance from the surface of the water to the gunwale.


Gaff: Spar which supports the upper side sofa fore-and-aft four-sided sail. Also, long-handed hook to bring fish aboard.
Gaff Rigged: A sailboat whose principal sail is supported by a gaff.
Galley: The kitchen area of a boat.
Gangway: The area of a ship’s side where people board and disembark.
Gear: A general term for ropes, blocks, tackle and other equipment.
Give-Way Boat: One that does not have the right-of-way and should avoid the stand-on boat.
Goto: A simple way of navigating straight to a waypoint or to the cursor position.
GPS: Global Positioning System. A satellite based navigation tool. This system is based on satellites in fixed orbits, circling the earth at an altitude of approximately 20,200 km. The system will provide the user with 24 hour a day all weather position coverage, with an accuracy of 5 to 30 meters.
Grab Rails: Hand-hold fittings mounted on cabin tops and sides for personal safety when moving around the boat.
Ground Tackle: A collective term for the anchor and its associated gear.
Ground tackle: An anchor and anchoring gear.
Gunwale: The part of a vessel where hull and deck meet. (Pronounced “gun’l”)


Halyard: Line for hoisting sails or flags.
Harbour: Hull
Hard Chine: An abrupt intersection between the hull side and the hull bottom of a boat so constructed.
Hatch: An opening in a boat’s deck fitted with a watertight cover.
Head: A boat’s toilet. Also the upper corner of a triangular sail. The foremost part of a vessel.
Head Up: Sailing closer to the wind.
Heading: The direction in which a vessel’s bow points at any given time.
Headway: The forward motion Finally, you want to know that your hard earned lolly is not going to some shady online casino site . of a boat. Opposite of sternway.
Heave: To throw, as to heave a line ashore. The rise and fall of a vessel in a seaway.
Helm: The wheel or tiller controlling the rudder.
Hitch: A knot used to secure a rope to another object or to another rope, or to form a loop or a noose in a rope.
Hold: A compartment below deck in a large vessel, used solely for carrying cargo.
Hull: The main body of a vessel exclusive of spars and rigging.


Inboard: More toward the center of a vessel; inside; a motor fitted inside a boat.
Instruments: Marine instruments enable the sailor to measure and plot various aspects of his on-the-water experience in real time. Typically these include performance indicators such as wind speed and direction, boat speed and heading, and depth. More sophisticated systems can then take these basic measurements and calculate and display additional information such as true and apparent wind speed, course over ground, speed over ground and much more. Marine instruments are generally a combination of sensor, processor and a relatively small display unit or dial which can be mounted both above and below deck.
Intracoastal Waterway: ICW: bays, rivers, and canals along the coasts (such as the Atlantic and Gulf of Mexico coasts), connected so that vessels may travel without going into the sea.
Irons: Yacht is pointing into the wind, sail is flapping and probably also going backwards.


Jacobs Ladder: A rope ladder, lowered from the deck, as when pilots or passengers come aboard.
Jetty: A structure, usually masonry, projecting out from the shore; a jetty may protect a harbour entrance.
Jib: Triangular Sail Set On A Stay Forward Of The Mast.
Jibe: Hanging sail from one side to another with wind astern.


Keel: The main structural member of a hull (backbone):underwater extension of hull to increase lateral resistance and stability.
Kicker (Also Called A Vang): A device used to keep the boom from rising.
Knot: A nautical mile-per-hour measure of speed. A nautical mile is approximately 6076 feed. (Astature mile is 5280 feet.) Also a means for joining two lines together or fastening a line to an object.


Latitude: The distance north or south of the equator measured and expressed in degrees.
Lay Line: The course on which your yacht, sailing close – hauled on starboard tack, can just make a windward mark which is to be rounded to port is the starboard – tack lay line for that mark, and the most windward line on which you would approach the mark on port tack is the port – tack lay line.
Lazarette: A storage space in a boat’s stern area.
Lee: The side sheltered from the wind.
Lee Shore: One onto which wind or current could force a boat.
Leeside or Leeward: The side opposite that from which the wind blows.
Leeway: The sideways movement of the boat caused by either wind or current.
Leg: The straight segments of a route between waypoints. A route with four waypoints has three legs.
Lie To: See heave to.
Line: Rope and cordage used aboard a vessel.
List: The leaning of a vessel to one side caused by misplaced gear or shifting cargo.
Log: A record of courses or operation. Also, a device to measure speed.
Longitude: The distance in degrees east or west of the meridian at Greenwich, England.
Lubber’s Line: A mark or permanent line on a compass indicating the direction forward parallel to the keel when properly installed.
Luff: Forward edge of a fore and aftsail.
Luffing: Pointing the yacht into the wind – sail flapping.


Magnetic Deviation: A local magnetic field on board a vessel. Can interfere with the earth’s magnetic field and create compass readings that may deviate from the actual magnetic heading. The deviation will vary with the actual heading.
Magnetic Heading: heading relative to magnetic north
Mainsheet: Line that controls the position of the mainsail
Mark (Buoy): An object the sailing instructions require a yacht to pass on a specified side.
Marlinespike Seamanship: General knowledge of knots, bends, hitches, splices and care of rope.
Marlinspike: A tool for opening the strands of a rope while splicing.
Mast: A pole usually going straight up from the deck (height can be tuned for different body weights), used to attach sail and boom.
MEA: National Marine Electronics Association.
Midship: Approximately in the location equally distant from the bow and stern.
MMSI: Maritime Mobile Service Identity. Unique identification number for a vessel, for use in Digital Selective Calling.
MOB: Man overboard.
MOB Function: Starts navigating back to the place where someone fell overboard.
Mooring: An arrangement for securing a boat to a mooring buoy or a pier.


Nautical Mile: One minute of latitude; approximately 6076 feet
Nautical Mile Nm: 1 nm is 1852 meters
Navigation: The art and science of conducting a boat safely from one point to another.
Navigation Rules: The regulations governing the movement of vessels in relation to each other, generally called steering and sailing rules.
Nmea0183: (NMEA0183) NMEA stands for National Marine Electronics Association (of the USA). NMEA 0183 was first introduced in 1983 as a voluntary industry standard for data communications among shipboard electronic devices. It uses a simple ASCII, serial communications protocol that defines how data is transmitted in a “sentence” from one ‘talker’ to one or more ‘listeners’ at a time, and therefore cannot be used to create networks. Data transmission is slow by today’s standard at 4800 bits / second and the standard does not allow for multiple ‘talkers’. However it is still in widespread use and is perfectly adequate for situations where one piece of equipment, for example a hand-held GPS, is to be connected to another such as an on-board chartplotter where the user wishes to integrate the two sets of data.
Nmea2000: (NMEA2000) Currently the accepted standard across the international marine industry, NMEA 2000 is much more sophisticated than NMEA 0183 in that it allows multiple units to simultaneously both transmit and receive data. With the inclusion of multifunction displays into a networked system the user can then choose any combination of data outputs to be displayed at any position or for any situation. It is NMEA 2000 that has made possible the development of the integrated navigation and control systems that are now being fitted on craft of almost every size and application.


Obstruction: An object that a yacht could not pass without changing course substantially to avoid it. e.g. a mark, a rescue boat, the shore, perceived underwater dangers or shallows.
Outboard: Toward or beyond the boat’s sides. A detachable engine mounted on a boat’s stern.
Outhaul: Line or device used to tension the foot of a sail.
Overboard: Over the side or out of the boat.


Painter: A line tied to the bow of a dinghy for towing or making fast.
Pay Out: Slacken or let outline.
Pennant: Emblematic flag.
Pier: A loading platform extending at an angle from the shore.
Piling: Support, protection for wharves, piers etc.; constructed of piles (see PILE)
Pitchpole: Capsize end over end.
Planing: A boat is said to be planing when it is essentially moving over the top of the water rather than through the water.
Planing Hull: A type of hull shaped to glide easily across the water at high speed.
Port: The left side of a boat looking forward. A harbour.
Port Side: Left (red)
Port Tack: Wind across the portside.
Privileged Vessel: A vessel which, according to the applicable Navigation Rule, has right-of-way (this term has been superseded by the term “stand-on”).


Quartering Sea: Sea coming on a boat’s quarter.


Range (Radar): The distance between the center of the radar image and the outer range ring. The scale is shown in the top left corner of the radar window.
Range Rings: Concentric circles extending from your boat (usually at the center of the radar window) and used to estimate distances to objects. The scale is shown in the top left corner of the radar window.
Reach: Point of sailing with wind near the beam.
Reaching: Sailing with the sail eased.
Reefing: Reducing the amount of sail area.
Relative Bearing: Direction of an object relative to a boat’s heading.
Rig: The arrangement of a yacht’s mast, sails and spars.
Rode: The anchor line and/or chain.
Route: Two or more waypoints linked in sequence to form a course for the boat.
Rudder: Underwater part of a boat used for steering.
Run: To allow a line to feed freely.
Running Lights: Lights required to be shown on boats underway between sundown and sunup.
Running: Sailing before the wind with the sail out.


Sail Trim: The position of the sails relative to the wind and desired point of sail. Sails that are not trimmed properly may not operate efficiently. Visible signs of trim are luffing, excessive heeling, and the flow of air past telltales. Also see sail shape.
Sand Bar: An area in shallow water where wave or current action has created a small, long hill of sand. Since they are created by water movement, they can move and may not be shown on a chart.
Satellite Navigation: A form of position finding using radio transmissions from satellites with sophisticated on-board automatic equipment.
Scope: Technically, the ratio of length of anchor rode in use to the vertical distance from the bow of the vessel to the bottom of the water. Usually six to seven to one for calm weather and more scope in storm conditions.
Screw: A boat’s propeller.
Scupper: An opening in a deck or cockpit permitting water to drain out.
SDGPS: Satellite Differential Global Positioning System – will provide position corrections from received satellite signals (WAAS, EGNOS and MSAS).
Sea Anchor: Device used for slowing a boat down, drogue.
Sea Cock: A through hull valve, a shut off on a plumbing or drain pipe between the vessel’s interior and the sea.
Sea Room: A safe distance from the shore or other hazards.
Seamanship: All the arts and skills of boat handling, ranging from maintenance and repairs to piloting, sail handling, marlinespike work, and rigging.
Seaworthy: A boat or a boat’s gear able to meet the usual sea conditions.
Secure: To make fast.
Set: Direction toward which the current is flowing.
Sextant: Navigational instrument used to determine the vertical position of a sky object such as the sun, moon or stars. Used with celestial navigation.
Sheet: Line used to position a sail relative to the wind.
Ship: A larger vessel usually thought of as being used for ocean travel. A vessel able to carry a “boat” on board.
Shroud: Standing rigging that supports a mast laterally.
Skeg: An extension of the keep for protection of propeller and rudder.
Slack: Not fastened; loose. Also, to loosen.
Slackwater: Minimum velocity of tidal current, sometimes abbreviated “slack”.
Smartcraft: A feature of Mercury Marine engines for monitoring engine performance.
Sole: Cabin or saloon floor. Timber extensions on the bottom of the rudder. Also the molded fiberglass deck of a cockpit.
Sonar-Echo-Sounder: An echo sounder, or ‘sonar’ in American terminology, is a sound-detecting instrument used to measure the distance between the surface of the water and objects in the water or on the ocean floor. An essential item of navigational and safety equipment, an echo sounder detects objects underwater by emitting a sound pulse via a transducer mounted on the hull or lowered to the required depth and then measuring the reflected echo. By using a set formula – bearing in mind that sound travels more slowly in fresh water than in sea water – the time lapse between emission and echo gives an accurate measurement of sea depth and other marine topography. Modern echo sounders can analyse the pulse return in order to display information including the composition of the sea bed, the presence of obstructions, and the location and size of fish in the water.
Sounder Status: A summary of echosounder settings.
Sounding: A measurement of the depth of water.
Spinnaker Pole: Sometimes called a spinnaker boom. A pole used to extend the foot of the spinnaker beyond the edge of the boat, and to secure the corner of the sail.
Spreader: Small spars extending toward the sides from one or more places along the mast. The shrouds cross the end of the spreaders, enabling the shrouds to better support the mast.
Spring Line: A pivot line used in docking, undocking, or to prevent the boat from moving forward or astern while made fast to a dock.
Spring Tide: The tide with the most variation in water level, occurring during new moons and full moons. This is the time of the highest high tide and the lowest low tide. The opposite of a neap tide.
Squall: A sudden, violent wind often accompanied by rain.
Square Knot: A knot used to join two lines of similar size. Also called a reef knot.
Standing Part: That part of a line which is made fast.The main part of a line as distinguished from the bight and the end.
Stand-On Boat: One that has the right of way and should maintain her course and speed.
Stand-On Vessel: That vessel which has right-of-way during a meeting, crossing, or overtaking situation.
Starboard: The right side of a boat when looking forward (green).
Starboard Tack: Wind across the starboard (right) side.
Stays: Standing rigging that supports a mast fore and aft.
Stem: The forward most part of the bow.
Stern Line: A docking line leading from the stern.
Stow: To put an item in its proper place.
Swamp: To fill with water, but not settle to the bottom.


Tacking: Changing direction by turning into the wind.
TCPA: Time to Closest Point of Approach. Time until the closest point of approach for two vessels.
Thwartships: At right angles to the centerline of the boat.
Tide: The periodic rise and fall of water level in the oceans.
Tiller: A bar or handle for turning a boat’s rudder or an outboard motor.
Topside: On or above a weather deck, a deck wholly exposed to the elements.
Transducer: The transducer serves as the acoustic “loudspeaker” and “microphone” to send and receive the signals through the water. They are most often made from ceramic elements carefully built into a robust housing. The ceramic elements change shape when a voltage is applied across them and they also generate a voltage when they encounter sound waves.
Transom: The stern cross-section of a square sterned boat.
Trim: The longitudinal balance of a boat. If either the bow or the stern is depressed,the vessel is said to be down by the bow or down by the stern. Also, to adjust the set of a sail.


Underway: Vessel in motion, i.e., when not moored, at anchor, or aground.
UTC: Universal Time Coordinates, which is equal to standard time in London (GMT). UTC is not affected by the local summertime adjustments.


V Bottom: A hull with the bottom section in the shape of a “V”.
Veer: Wind veers when its direction changes clockwise.
VMG: Velocity Made Good. A vessel’s true progress towards a waypoint taken into consideration all factors like leeway and current.


Wake: Moving waves, track or path that a boat leaves behind it, when moving across the waters.
Wash: The rush or sweeping of waves on a bank, shore or vessel.
Way: Movement of a vessel through the water such as headway, sternway orleeway.
Waypoint: A discrete point, stored in a navigator, located on the surface of the earth. Normally this point will be identified by Lat/Lon coordinates although in some systems it may be shown by T.D.’s.
Wharf: Manmade structure parallel to the shoreline for loading, unloading or making fast.
Whipping: Method of binding the end of a rope with small twine.
Windward: Toward the direction from which the wind is coming.


Yacht: A pleasure vessel, a pleasure boat.
Yaw: To swing or steer off course, as when running with a quartering sea.