392 sailing, navigation, VHF radio and yachting terms — written for modern cruising sailors,
charter crews and skipper exam candidates. Last updated April 2026.
Automatic Identification System — a VHF-based transponder network that continuously broadcasts a vessel's identity, position, course, and speed to other AIS-equipped craft and to shore stations, greatly improving collision awareness.
A personal AIS man-overboard beacon that, when activated (usually automatically on immersion), transmits the casualty's GPS position as an AIS distress target visible on every nearby AIS receiver.
An engine-driven generator that converts mechanical rotation into alternating current, which on a yacht is then rectified to charge the house and starter batteries while the engine runs.
An electric or manual winch mounted on the foredeck that hauls and lowers the anchor chain or rode, typically with a gypsy for chain and a drum for warp.
Automatic Radar Plotting Aid — radar software that tracks targets automatically and computes CPA (closest point of approach) and TCPA (time to CPA) to flag collision risk.
A downwind sail (also called a cruising chute or gennaker) with a fixed tack but no pole, cut asymmetrically so it can be set and trimmed like a large genoa on a reach.
An electronic self-steering system that uses a heading or GPS input to drive a hydraulic ram, linear drive, or wheel motor, holding the boat on course without a human helm.
An instrument that integrates current flow over time to report the true state of charge and remaining amp-hours of a battery bank, far more accurately than voltage alone.
A manual or electric pump fitted to remove water from the bilge; most cruising yachts carry at least one of each type, with the electric pump often wired to an automatic float switch.
A tackle (also called a kicking strap) running from the base of the mast to the boom, pulling the boom down to flatten the mainsail and control leech twist.
A small transverse propeller mounted in a tunnel near the bow that pushes the bow sideways at low speed, making close-quarters manoeuvring much easier.
The former term (replaced in modern COLREGs usage by 'give-way vessel') for the vessel obliged to keep out of the way in a crossing or overtaking situation.
In the IALA Region B buoyage system (USA, parts of the Americas, Japan, Korea, Philippines), an odd-numbered green cylindrical buoy marking the port side of a channel when entering from seaward.
An electronic display that overlays the vessel's GPS position on digital charts, and often integrates AIS, radar, sonar, and autopilot data on the same screen.
A very flat, large, reaching sail set on a continuous-line furler forward of the forestay; it fills the gap between a genoa and an asymmetric spinnaker in light upwind-to-close-reaching conditions.
The International Regulations for Preventing Collisions at Sea (1972, amended) — the body of rules governing rights of way, lights, shapes, and sound signals at sea.
To reduce the drive produced by the sails, by (1) pinching into the wind so the sails luff, (2) easing sheets to let the sails flutter, or (3) over-trimming so airflow detaches and stalls.
An electronic instrument (also called an echo sounder) that measures depth below the transducer by timing an ultrasonic pulse's reflection from the seabed.
A traditional Arabian sailing craft, typically single- or twin-masted and carrying lateen sails, still seen throughout the Red Sea and western Indian Ocean.
A long cone or series of small cones streamed on a bridle from the stern in very heavy weather to slow the boat, keep her stern-to the seas, and prevent broaching. Distinct from a sea anchor.
Digital Selective Calling — a feature of modern VHF and SSB radios that allows a pre-formatted digital distress alert, including the boat's identity and GPS position, to be transmitted at the press of a button.
A brand of ultra-high-molecular-weight polyethylene (UHMWPE) fibre; as strong as steel wire but a fraction of the weight, now widely used for halyards, sheets, and even standing rigging.
Electronic Chart Display and Information System — a type-approved electronic charting system accepted as the primary means of navigation on many commercial vessels, using ENC vector charts.
Emergency Position Indicating Radio Beacon — a self-contained 406 MHz satellite distress beacon registered to the vessel, activated manually or by a hydrostatic release, which alerts the global Cospas-Sarsat system.
A portable pressure-charged bottle used to fight fire on board; yachts typically carry Class A, B, and E/C types to cover solids, liquids, and electrical fires respectively.
A pyrotechnic distress signal — handheld red flares are for close-range visibility, parachute red flares for long-range, and orange hand smokes for daylight surface signalling.
A device fitted in the shore-power earth conductor to block low-voltage galvanic currents that would otherwise corrode underwater metals while connected to a marina.
A ranking of metals by their tendency to corrode in a given electrolyte (typically seawater); used to choose compatible fasteners, fittings, and sacrificial anodes.
Global Maritime Distress and Safety System — the integrated network of satellite and terrestrial radio services (VHF-DSC, MF/HF-DSC, Inmarsat, EPIRB, SART) that coordinates maritime distress alerting and search and rescue.
Global Navigation Satellite System — the umbrella term covering all satellite positioning constellations: GPS (USA), GLONASS (Russia), Galileo (EU), and BeiDou (China).
Global Positioning System — the US satellite constellation whose signals let a receiver compute its position, heading, and speed over ground almost anywhere on Earth; today typically combined with other GNSS signals for better accuracy.
A watertight bag pre-packed with survival essentials (flares, water, food, EPIRB, handheld VHF, passports, etc.) that is grabbed on the way to the liferaft in an abandon-ship emergency.
The shortest path between two points on the Earth's surface — an arc of a circle whose plane passes through the centre of the Earth. Used for long ocean passages.
A compact binary weather-data format (Gridded Binary) used to download forecast wind, pressure, waves, and currents for display on board in GRIB-capable navigation software.
To balance the boat almost stationary by backing the headsail, lashing the helm to leeward, and trimming the main so the rig and rudder cancel each other out.
Describing a vessel that has completed the heaving-to process and is sitting more or less stationary with backed jib, eased main, and helm held to leeward.
A global satellite network (e.g. Iridium Go!, Iridium Certus) widely used by offshore sailors for voice, SMS, weather downloads, and low-bandwidth email anywhere on Earth.
A wire, webbing strap, or spliced rope run fore-and-aft along each sidedeck, to which a safety harness tether can be clipped so the crew stays attached when moving around.
The weighted vertical fin beneath the hull that resists leeway and, through its ballast, keeps the boat upright; modern variants include fin, bulb, winged, lifting, swing, and twin keels.
A sail made of composite panels — typically film-over-fibre (e.g. Dacron, polyester, Kevlar, or carbon) laminated together — offering better shape-holding than woven cloth.
A network of light lines running from the upper mast down to the boom that cradles the mainsail as it is lowered, stopping it from spilling onto the deck.
A self-inflating, canister- or valise-packed survival craft launched in an abandon-ship situation; modern ISO-standard rafts carry water, flares, a sea anchor, and other survival gear.
A buoyant horseshoe-shaped sling on a floating line, deployed to trail astern during a man-overboard recovery so the casualty can be reached and hauled alongside.
(1) The aerodynamic or hydrodynamic force generated by a sail or keel that drives the boat through the water. (2) A windshift that lets the boat head up higher than before.
A modern lithium iron phosphate house battery offering far greater usable capacity, deeper cycling, faster charging, and longer life than lead-acid, at higher purchase cost and with specific charging and BMS requirements.
Multi-Function Display — a large chartplotter screen able to show radar, AIS, sonar, engine data, camera feeds, and charts, usually linked by NMEA 2000 or Ethernet.
Maritime Mobile Service Identity — a unique nine-digit number issued to each DSC-VHF/HF radio, EPIRB, or AIS transponder, used to identify the vessel in digital distress and routine calls.
A dedicated button on a GPS, chartplotter, or autopilot that marks the current position the instant a person goes overboard, giving an immediate waypoint to navigate back to.
Maximum Power Point Tracking charge controller — an electronic regulator that continuously matches a solar panel's output to the battery, extracting 20–30 % more energy than a simple PWM controller.
A legacy serial data standard defined by the US National Marine Electronics Association, used to send sentences (e.g. GPS position, heading, depth) between instruments at 4800 baud.
A modern CAN-bus data network for marine electronics, allowing plug-and-play interconnection of GPS, wind, depth, engine, autopilot, and MFDs on a single backbone.
In the IALA Region B system, a red even-numbered conical buoy marking the starboard side of a channel when entering from seaward, usually paired with green cans on the opposite side.
A proprietary symmetric downwind sail with a horizontal aerofoil slot through the middle, giving lift and stability and making shorthanded downwind passages easier.
Personal Locator Beacon — a small 406 MHz satellite distress beacon registered to an individual (not a vessel), carried on a lifejacket or harness for personal survival use.
A microwave ranging system that bounces a rotating pulse off targets and displays their bearing and range; modern broadband/pulse-compression radars resolve close targets at very low power, often with MARPA/ARPA target tracking.
A course line crossing all meridians at the same angle — a straight line on a Mercator chart, suitable for passages up to a few hundred miles; for longer distances a Great Circle is shorter.
Search and Rescue Transponder — an emergency device that, when triggered by an X-band radar pulse, replies with a 12-dot signature on a searching vessel's radar screen, guiding rescuers to the liferaft.
A large parachute-like drogue streamed from the bow on a long rode in survival conditions to hold the vessel head-to-sea and dramatically slow any drift. Distinct from a stern drogue.
A through-hull valve that can be opened or closed to admit water to, or prevent water from entering, the boat through engine, heads, galley, or cockpit drain fittings.
A small headsail fitted with a track across the foredeck so the sheet travels automatically from side to side when the boat tacks, eliminating the need to trim headsails on each tack.
120/230 V AC supplied from a marina pedestal through a dedicated inlet and cable, used to run onboard AC appliances and to drive the battery charger while alongside.
A traditional reefing method (also called jiffy reefing) in which the tack and clew reef cringles are pulled down to fixed points on the mast and boom, and the surplus cloth is gathered.
A fabric tube with a hoop that slides down over an asymmetric or symmetric spinnaker, smothering the sail from the top to make hoisting and dousing safe and manageable shorthanded.
A photovoltaic array — rigid glass, semi-flexible, or flexible — that converts sunlight to DC current to charge the house bank, commonly 100–400 W on cruising yachts.
A marine MF/HF single-side-band transceiver that, under the right conditions, can reach thousands of miles — historically used for ocean weather nets, email (e.g. via Pactor modem) and long-range distress; now largely superseded by satellite for cruising sailors.
Sailing with the wind coming over the starboard side; under COLREGs, a starboard-tack sailing vessel normally has right of way over a port-tack vessel.
A low-Earth-orbit satellite broadband system widely adopted on cruising and commercial vessels since the mid-2020s for high-speed internet at sea, replacing older geostationary Fleet and V-SAT services on many yachts.
A small, extra-heavy, high-visibility foresail set in survival conditions — ideally on a removable inner stay — to balance the rig under trysail or triple-reefed main.
(1) To turn the bow through the eye of the wind so the boat changes from one close-hauled course to the other. (2) The forward lower corner of a fore-and-aft sail.
A two- or three-hook safety line attaching a crew member's lifejacket/harness to a jackline or strongpoint, preventing separation from the boat if they fall or are washed down.
A small, heavy, triangular storm sail that replaces the mainsail on its own track or separate track in survival conditions when the boom is inadvisable or unsafe.
Under international rules a vessel is 'underway' whenever she is not at anchor, moored, aground, or made fast to the shore — even if she is not currently moving through the water.
A line-of-sight very-high-frequency marine radio, usually with DSC, used for routine, safety, urgency, and distress traffic; range is typically 20–40 NM between ships, further to a high coast station.
A reverse-osmosis desalinator that forces seawater through a semi-permeable membrane at high pressure to produce drinking-quality fresh water on board.
The boat's tendency to turn into the wind if the helm is released; some is desirable for feel and safety, but excessive weather helm signals an overpowered or mis-trimmed rig.
The practice — today usually software-assisted using GRIB forecasts and the boat's polars — of choosing a passage track that optimises for weather, sea state, and ETA.
A drum with a handle (manual) or motor (electric/hydraulic) that provides mechanical advantage when sheeting or hoisting; self-tailing winches feed the line off automatically.
A mast- or pole-mounted propeller-driven turbine that converts apparent-wind energy into battery charging current — complementary to solar on extended cruising yachts.
A two-masted rig similar to a ketch but with the (smaller) mizzenmast stepped aft of the rudder post; the mizzen is used mainly for balance rather than drive.
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