Glossary

A pivoted support that allows an object, such as a compass or a stove, to remain level regardless of the motion of the vessel.

A gimbal is a...

In a collision situation, one or more vessels are defined as Give Way. The Give Way vessel should alter its course to concede passage to another...

A term that collectively refers to the three organisations responsible for maintaining maritime navigation aids—such as lighthouses, buoys, and...

A composite material made of a polymer matrix reinforced with fine glass fibres, commonly used in marine applications for its strength,...

This shape represents the Letter G (Flag Semaphore) and the Number 7 (Flag Semaphore).

International Morse Code sequence representing the letter G.

A weather model developed by the National Centers for Environmental Prediction (NCEP) that provides global weather forecasts by simulating the...

An internationally agreed-upon set of safety procedures, communication protocols, and equipment designed to ensure that ships at sea can send and...

A map of the UK indicating the 3 sea areas around the coast and the coast of nearby European countries. White pointers indicate Medium Frequency...

The collective set of systems that enables positioning devices to calculate latitude & longitude. The system includes solutions including the GPS...

The US-based system of satellites, able to determine the latitude and longitude of a receiver on Earth by calculating the time difference for...

An internationally agreed-upon set of safety procedures, communication protocols, and equipment designed to ensure that ships at sea can send and...

The mean solar time at the Prime Meridian in Greenwich, London, used as a global time standard.

Greenwich Mean Time (GMT) is a timekeeping...

A type of map projection where the surface of the Earth is projected onto a plane from the centre of the globe, causing great circles to appear...

The collective set of systems that enables positioning devices to calculate latitude & longitude. The system includes solutions including the GPS...

Pronounced: GOLF

The term for the letter G in the NATO Phonetic Alphabet.

A pivotal fitting on a sailing vessel that connects the boom to the mast, allowing for controlled movement in multiple directions.

The...

A sailing configuration where a fore-and-aft rigged vessel's sails are set on opposite sides of the boat, typically with the mainsail on one side...

The US-based system of satellites, able to determine the latitude and longitude of a receiver on Earth by calculating the time difference for...

The mean solar time at the Prime Meridian in Greenwich, London, used as a global time standard.

Greenwich Mean Time (GMT) is a timekeeping...

A type of data format used in oceanography and meteorology to represent gridded data in a binary form for efficient storage and...

A type of data format used in oceanography and meteorology to represent gridded data in a binary form for efficient storage and...

A composite material made of a polymer matrix reinforced with fine glass fibres, commonly used in marine applications for its strength,...

A safety barrier installed along the edges of a vessel’s deck to prevent crew or passengers from falling overboard.

This essential feature on...

The upper edge or rim of a boat's side, often serving as a structural reinforcement and a mounting point for fittings or equipment.

The term...

A rope, wire, or chain used to stabilise or secure a mast, spar, or other structure on a vessel by counteracting lateral forces.

A guy is a...

A gybe (jibe) is a sailing manoeuvre where a boat changes direction by turning its stern through the wind. During a gybe, the wind crosses over...

A line or rope used to hoist or lower a sail, flag, or spar on a boat.

The term "halyard" comes from the phrase "haul yard," which refers to...

A hand-bearing compass is a portable compass held in the hand that is used to take bearings of objects or landmarks to determine their location...

A hand-held pyrotechnic signalling device that produces a bright light and smoke when ignited, used for distress signalling at sea. 

Hand-held...

A handrail is a rail designed to be grasped by the hand for support and stability. On a typical sailing yacht, one is usually mounted on the...

A fitting or clip used to attach a sail, typically a headsail, to a stay or forestay on a sailing vessel.

A hank is a small, often metal or...

A sheltered body of water where vessels can anchor or dock, offering protection from the elements, often also where ports are, providing...

The highest level of sea water that can be predicted to occur under average meteorological conditions and under any combination of astronomical...

An opening in the deck or bulkhead of a vessel, typically covered by a door or lid, providing access to the space below.

A hatch is a crucial...

The International Maritime Signal Flag Hotel.

Meaning

I have a pilot on board.

Used in satellite navigation and positioning systems to quantify the accuracy of horizontal position measurements. It is a unitless factor that...

Head (heads) refers to the toilet or bathroom on a boat. The heads on a boat may be equipped with a marine toilet designed to safely handle waste...

The direction in which a vessel's bow is pointed at any given moment, typically measured in degrees relative to true north or magnetic...

A coastal landform characterised by a high, narrow piece of land that juts out into the sea, often forming a prominent point along the...

A headsail is a sail set forward of the mast on a sailboat. It is typically smaller than the mainsail and is used to help propel the boat forward...

Sea area of the Met Office Shipping Forecast. Covers waters around the Hebridean islands off western Scotland.

Covering the Hebridean...

Tilt or lean to one side, typically due to wind pressure on a sailing vessel's sails.

The term "heel" is widely used in recreational and...

The vertical distance from the water's surface at Mean High Water Springs to the focal plane of a lighthouse's light source.

Height of Light...

The vertical distance between the water's surface at any given time and the established chart datum, typically the lowest astronomical...

To steer or direct a vessel using its helm or steering apparatus. The apparatus or position used to steer and control a vessel, typically...

The individual responsible for steering and navigating a vessel, ensuring it maintains its intended course.

A helmsman plays a crucial role in...

The radio frequency range between 3 and 30 megahertz (MHz), commonly used for long-range marine communications via skywave propagation. 

High...

The highest level of sea water that can be predicted to occur under average meteorological conditions and under any combination of astronomical...

The radio frequency range between 3 and 30 megahertz (MHz), commonly used for long-range marine communications via skywave propagation. 

High...

The UK government agency responsible for producing astronomical and navigational data for maritime and military use. 

His Majesty's Nautical...

A knot that attaches a rope to an object, such as a post, ring, or other rope.

A hitch is a versatile and essential knot where securing a rope...

This shape represents the Letter H (Flag Semaphore) and the Number 8 (Flag Semaphore).

International Morse Code sequence representing the letter H.

The organisation responsible for search and rescue operations in UK waters.

His Majesty's Coastguard (HMCG) is a section of...

The UK government agency responsible for producing astronomical and navigational data for maritime and military use. 

His Majesty's Nautical...

To raise an object vertically, commonly a sail or flag, using a halyard.

It typically uses a system of ropes, cables, pulleys, and sometimes a...

A sealed onboard container designed to temporarily store wastewater, such as sewage or greywater, until it can be properly discharged at a...

Used in satellite navigation and positioning systems to quantify the accuracy of horizontal position measurements. It is a unitless factor that...

A U-shaped flotation device designed to be thrown to a person overboard to provide buoyancy and aid in rescue.

The horseshoe lifebuoy, also...

Pronounced: hoh-TELL

The term for the letter H in the NATO Phonetic Alphabet.

The watertight body or shell of a boat or ship, excluding the deck, rigging, and other superstructures.

The hull is the fundamental structure...

Sea area of the Met Office Shipping Forecast. Lies off the east coast of England, near the Humber Estuary.

Named for the Humber Estuary...

Beaufort Scale - Force 12 (Hurricane Force 12)

Hurricane-force is a term used to describe wind speeds equal to or greater than 64 knots (74...

A lifting surface or structure mounted beneath a vessel's hull that, when moving through water, generates lift to raise the hull above the...

The International Association of Lighthouse Authorities (IALA) is an international organisation that aims to promote safe, efficient, and...

An official document that certifies a person's ability to operate a pleasure craft in countries that recognise it. 

The International...

The International Maritime Signal Flag India.

Meaning

I am altering course to port.

A numerical weather prediction model that uses a grid system based on an icosahedron to simulate atmospheric processes with high resolution and...

A numerical weather prediction model that uses a grid system based on an icosahedron to simulate atmospheric processes with high resolution and...

A system of flags, codes, and symbols used by ships to communicate essential messages and ensure safety at sea, regardless of language...

An imaginary longitudinal line located at approximately 180 degrees longitude serving as the demarcation where the calendar date changes by one...

An intergovernmental organisation dedicated to ensuring the uniformity and standardisation of hydrographic and nautical charting practices...

This shape represents the Letter I (Flag Semaphore) and the Number 9 (Flag Semaphore).

International Morse Code sequence representing the letter I.

A specialised agency of the United Nations headquartered in London and responsible for regulating shipping, the IMO has 175 Member States.

The...

An impeller is a rotating component within a pump or compressor that is used to impart motion to a fluid. It typically consists of blades or...

Pronounced: IN-dee-ah

The term for the letter I in the NATO Phonetic Alphabet.

A line or tackle used to pull a sail or spar inboard, typically to adjust sail shape or reduce projection beyond the hull.

An in hauler is a...

A situation where a sailing vessel is stalled with its bow pointed directly into the wind, making it difficult to manoeuvre or gain forward...