Glossary
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TermDefinition
- General Nautical Terminology Halyard
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...
More Details - General Nautical Terminology Hand Bearing Compass
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...
More Details - General Nautical Terminology, Safety Hand-held Flare
A hand-held pyrotechnic signalling device that produces a bright light and smoke when ignited, used for distress signalling at sea.
Hand-held...
More Details - General Nautical Terminology Handrail
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...
More Details - General Nautical Terminology Handy BillyA loose block and tackle with a hook or tail on each end, which can be used wherever it is needed. Usually made up of one single and one double block.
- General Nautical Terminology Hank
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...
More Details - General Nautical Terminology Harbour
A sheltered body of water where vessels can anchor or dock, offering protection from the elements, often also where ports are, providing...
More Details - General Nautical Terminology Harden InTo haul in the sheets to bring the sail closer to the centreline; the opposite of ease out
- General Nautical Terminology Harden UpTurn towards the wind; sail closer to the wind.
- General Nautical Terminology, Navigation HAT
The highest level of sea water that can be predicted to occur under average meteorological conditions and under any combination of astronomical...
More Details - General Nautical Terminology Hatch
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...
More Details - General Nautical Terminology Haul InTo pull in, usually a sheet, halyard or anchor line
- Flag / Pennant, Signals & Communication Code Flag Hotel (H)

The International Maritime Signal Flag Hotel.
Meaning
I have a pilot on board.
- General Nautical Terminology, Navigation HDOP
Used in satellite navigation and positioning systems to quantify the accuracy of horizontal position measurements. It is a unitless factor that...
More Details - General Nautical Terminology Head
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...
More Details - General Nautical Terminology, Navigation Heading
The direction in which a vessel's bow is pointed at any given moment, typically measured in degrees relative to true north or magnetic...
More Details - General Nautical Terminology, Navigation Headland
A coastal landform characterised by a high, narrow piece of land that juts out into the sea, often forming a prominent point along the...
More Details - General Nautical Terminology Headsail
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...
More Details - General Nautical Terminology Head to WindTo point the stem of the vessel into the wind
- General Nautical Terminology HeadwayMovement through the water stem first
- General Nautical Terminology Heave To More Details
- General Nautical Terminology, Weather (Meteorology) Hebrides
Sea area of the Met Office Shipping Forecast. Covers waters around the Hebridean islands off western Scotland.
Covering the Hebridean...
More Details - General Nautical Terminology Heel
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...
More Details - General Nautical Terminology, Navigation Height of Light
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...
More Details - General Nautical Terminology, Navigation Height of Tide
The vertical distance between the water's surface at any given time and the established chart datum, typically the lowest astronomical...
More Details - General Nautical Terminology, Parts of a Boat Helm
To steer or direct a vessel using its helm or steering apparatus. The apparatus or position used to steer and control a vessel, typically...
More Details - General Nautical Terminology Helmsman
The individual responsible for steering and navigating a vessel, ensuring it maintains its intended course.
A helmsman plays a crucial role in...
More Details - Courses, RYA Helmsman's PracticalThe RYA Helmsman’s Practical course is designed to build confidence and competence in handling motorboats. Participants learn essential skills... More Details
- General Nautical Terminology, Signals & Communication HF
The radio frequency range between 3 and 30 megahertz (MHz), commonly used for long-range marine communications via skywave propagation.
High...
More Details - General Nautical Terminology, Navigation Highest Astronomical Tide (HAT)
The highest level of sea water that can be predicted to occur under average meteorological conditions and under any combination of astronomical...
More Details - General Nautical Terminology, Signals & Communication High Frequency (HF)
The radio frequency range between 3 and 30 megahertz (MHz), commonly used for long-range marine communications via skywave propagation.
High...
More Details - Organisation His Majesty's Nautical Almanac Office (HMNAO)
The UK government agency responsible for producing astronomical and navigational data for maritime and military use.
His Majesty's Nautical...
More Details - General Nautical Terminology, Knot Hitch
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...
More Details - Flag Semaphore, Signals & Communication Letter H (Flag Semaphore)

This shape represents the Letter H (Flag Semaphore) and the Number 8 (Flag Semaphore).
- Morse Code, Signals & Communication Letter H (Morse Code)
International Morse Code sequence representing the letter H.
- Organisation HMCG
The organisation responsible for search and rescue operations in UK waters.
His Majesty's Coastguard (HMCG) is a section of...
More Details - Organisation HMNAO
The UK government agency responsible for producing astronomical and navigational data for maritime and military use.
His Majesty's Nautical...
More Details - General Nautical Terminology Hoist
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...
More Details - General Nautical Terminology Holding Tank
A sealed onboard container designed to temporarily store wastewater, such as sewage or greywater, until it can be properly discharged at a...
More Details - General Nautical Terminology, Navigation Horizontal Dilution of Precision (HDOP)
Used in satellite navigation and positioning systems to quantify the accuracy of horizontal position measurements. It is a unitless factor that...
More Details - General Nautical Terminology, Safety Horseshoe Lifebuoy
A U-shaped flotation device designed to be thrown to a person overboard to provide buoyancy and aid in rescue.
The horseshoe lifebuoy, also...
More Details - Phonetic Alphabet, Signals & Communication Hotel
Pronounced: hoh-TELL
The term for the letter H in the NATO Phonetic Alphabet.
- General Nautical Terminology HoundsAttachments of stays to masts.
- General Nautical Terminology House flagAny personal flag or club flag flown from starboard spreaders or flagstaff.
- General Nautical Terminology Hull
The watertight body or shell of a boat or ship, excluding the deck, rigging, and other superstructures.
The hull is the fundamental structure...
More Details - General Nautical Terminology Hull SpeedThe maximum efficient speed of a displacement-hulled vessel.
- General Nautical Terminology, Weather (Meteorology) Humber
Sea area of the Met Office Shipping Forecast. Lies off the east coast of England, near the Humber Estuary.
Named for the Humber Estuary...
More Details - General Nautical Terminology, Weather (Meteorology) Hurricane Force
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...
More Details - General Nautical Terminology Hydrofoil
A lifting surface or structure mounted beneath a vessel's hull that, when moving through water, generates lift to raise the hull above the...
More Details - General Nautical Terminology HydrographyThe science of surveying the waters of the earth and adjacent land area, and publishing the results in charts, pilots, etc, for example Admiralty... More Details

