Glossary

Sea area of the Met Office Shipping Forecast. Covers waters off southeast England, centered on the Thames Estuary.

From the River Thames...

An internationally renowned professional institution representing naval architects and marine engineers worldwide. It was founded in 1860 and is...

Substitute or repeater flags allow messages with duplicate characters to be signalled without requiring multiple sets of flags.

The phrase “three sheets to the wind” comes straight from nautical life—and originally had nothing to do with drinking at all!

🚢 Nautical...

The horizontal movement of water caused by the rise and fall of the tide.

A tidal stream refers to the flow of water generated by the...

A collection of charts that depict the set (direction) and rate (speed) of tidal currents at various stages of the tidal cycle.

A Tidal Stream...

The rise and fall of sea levels caused by the gravitational forces of the moon and the sun acting on the Earth's oceans. Tides are characterised...

Charts or listings that provide the predicted times and heights of high and low tides for specific coastal locations over a given period.

Tide...

A measure used in satellite navigation systems, such as GPS, to quantify the effect of errors in the timing of satellite signals on the accuracy...

A measure used primarily in maritime and aviation contexts to estimate the time until two moving objects (e.g., ships or aircraft) reach their...

A region of the Earth where the same standard time is used.

A time zone is a geographical area that observes a uniform standard time for...

Flag semaphore indicating the letter T.

International Morse Code sequence representing the letter T.

A low, raised edge running along the outer perimeter of a boat's deck, designed to provide footing stability and prevent gear or crew from...

A line or wire used to support the boom of a sailboat when the sail is not hoisted, or to adjust the height of a spinnaker pole. 

A topping...

The outer hull of a vessel above the waterline, extending from the deck to the water's edge.

The term "topsides" is a fundamental concept in...

Sea area of the Met Office Shipping Forecast. Located off the southern coast of Spain, near Cape Trafalgar.

Named after Cape Trafalgar (site of...

A navigation system designed to organise the flow of vessel traffic in congested or high-risk areas, ensuring safe passage by separating opposing...

The transom is the flat, vertical surface at the back of a boat. It is typically where the outboard motor or stern drive is attached to a motor...

A sliding fitting or track on a sailing vessel, used to adjust the position of a sail's sheet or other control lines for optimal sail...

Trim is the adjustment of a boat's sails, weight distribution, and angle relative to the water to optimise performance, balance, and...

Trinity House is a maritime organisation responsible for maintaining navigational aids, including lighthouses and buoys, along England, Wales,...

A tropical hurricane is an intense tropical cyclone characterised by strong winds, heavy rainfall, and low pressure. These storms typically form...

True North refers to the geographic direction towards the Earth’s geographic North Pole. The direction along the Earth’s surface points directly...

A navigation system designed to organise the flow of vessel traffic in congested or high-risk areas, ensuring safe passage by separating opposing...

When a rope passes around an object, such as a post, when tying a knot.

Sea area of the Met Office Shipping Forecast. Covers the southwestern North Sea, off the River Tyne estuary in northeast England.

From the River...

A region of the Earth where the same standard time is used.

A time zone is a geographical area that observes a uniform standard time for...

The International Maritime Signal Flag Uniform.

Meaning

You are running into danger.

The UK government agency responsible for producing nautical charts, publications, and navigational information to support safe maritime...

The UK government agency responsible for producing nautical charts, publications, and navigational information to support safe maritime...

The global numerical weather prediction model developed by the United Kingdom Met Office, providing forecasts for various weather parameters...

The global numerical weather prediction model developed by the United Kingdom Met Office, providing forecasts for various weather parameters...

A high-resolution numerical weather prediction model used by the UK Met Office to provide detailed weather forecasts for the United Kingdom and...

Flag semaphore indicating the letter U.

International Morse Code sequence representing the letter U.

Ultraviolet (UV) light is a type of electromagnetic radiation with a wavelength shorter than visible light but longer than X-rays. In the marine...

An international organisation founded in 1945 aimed at promoting peace, security, and cooperation among countries worldwide.

The United...

A loop which crosses under the standing part of a rope when tying a knot.

Under the weather is commonly used to describe feeling ill or unwell. Its origins can be traced back to maritime language. It originated from the...

Underway refers to vessels not anchored or made fast to the shore (for example, a marina or mooring buoy). The vessel may be moving due to the...

Pronounced: YOU-nee-form

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

A high-resolution numerical weather prediction model used by the UK Met Office to provide detailed weather forecasts for the United Kingdom and...

An international organisation founded in 1945 aimed at promoting peace, security, and cooperation among countries worldwide.

The United...

A scientific institution operated by the United States Navy that specialises in astronomical and timekeeping research, providing precise...

A United States Armed Forces branch, responsible for maritime safety, security, and environmental stewardship in domestic and international...

A United States Armed Forces branch, responsible for maritime safety, security, and environmental stewardship in domestic and international...

A scientific institution operated by the United States Navy that specialises in astronomical and timekeeping research, providing precise...

The primary time standard by which the world regulates clocks and time serving as the basis for civil time globally.

Coordinated Universal...

Ultraviolet (UV) light is a type of electromagnetic radiation with a wavelength shorter than visible light but longer than X-rays. In the marine...

A line or tackle system used to control the angle of a boom on a sailing vessel, preventing it from lifting and stabilising the sail.

The...

The maximum angle of heel at which a vessel can recover to an upright position without capsizing.

The vanishing angle is a critical concept in...

The angular difference between true north and magnetic north, also known as magnetic declination, which affects compass readings.

Variation is...

The International Maritime Signal Flag Victor.

Meaning

I require assistance.
If appended with a Numeral Pennant, Velocity in kilometres...

A measure used in satellite navigation systems, such as GPS, to quantify the impact of satellite geometry on vertical positioning accuracy. It...

A digital nautical chart that represents navigational data using vector graphics, allowing for scalable and interactive mapping of maritime...

The speed at which a vessel is effectively moving towards its intended destination, factoring in both its current speed and the angle of travel...

A measure used in satellite navigation systems, such as GPS, to quantify the impact of satellite geometry on vertical positioning accuracy. It...

A range of radio frequencies from 30 MHz to 300 MHz, commonly used in marine communication for short-range, line-of-sight transmissions.

Very...

Any craft designed for transportation on water, including ships, boats, and other waterborne vehicles.

A vessel is any structure or craft...

A shore-based system that monitors and manages vessel movements in busy or hazardous waterways to enhance safety, efficiency, and environmental...

A range of radio frequencies from 30 MHz to 300 MHz, commonly used in marine communication for short-range, line-of-sight transmissions.

Very...

A communication device that operates on Very High Frequency (VHF) radio waves, used for ship-to-ship, ship-to-shore, and emergency maritime...

Pronounced: VIK-tah

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

The process or system of provisioning a ship with necessary supplies, especially food and drink, for the crew's sustenance during a...

Sea area of the Met Office Shipping Forecast. This area covers the northernmost part of the North Sea, off the east coast of the UK and west...

Beaufort Scale - Force 11

A violent storm is a weather phenomenon characterised by strong winds exceeding 64 knots (74 miles per hour) and...

Flag semaphore indicating the letter V.

International Morse Code sequence representing the letter V.

The speed at which a vessel is effectively moving towards its intended destination, factoring in both its current speed and the angle of travel...

A shore-based system that monitors and manages vessel movements in busy or hazardous waterways to enhance safety, efficiency, and environmental...

A strong rope or line used for mooring, towing, or manoeuvring a vessel, particularly in situations requiring precise control. 

Warping is a...

A designated period during which a specific crew member or group is responsible for the safe operation and navigation of the vessel.

In...

The vessel’s course through the water, derived from the compass course steered, allowing for leeway but not tide. A line representing the water...

Speed, progress, or momentum through the water. More technically, the point at which there is sufficient water flow past a vessel's rudder for it...

A specific location or reference point on a navigational route, often used to mark progress or changes in course.

A waypoint is a...

The International Maritime Signal Flag Whiskey.

Meaning

I require medical assistance.

The tendency of a sailing vessel to turn windward (towards the wind) when under sail, requiring corrective steering to maintain a desired...

To lift the anchor from the seabed in preparation for setting sail or moving a vessel.

Weighing anchor is a fundamental nautical action that...

A standard in satellite-derived positions. Charts will indicate if they are calibrated to WGS84 or another system.

WGS84 is the standard...

To bind the end of a rope with small cord or twine to prevent it from fraying.

Whipping is a traditional and essential technique in ropework,...

Pronounced: WISS-key

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

Beaufort Scale – Force 10

A Whole Gale is a term used in meteorology to describe a wind of force 10 on the Beaufort scale, corresponding to...

Sea area of the Met Office Shipping Forecast. Covers the Solent and waters around the Isle of Wight off southern England.

After the Isle of...

A mechanical device used on boats to haul in or let out heavy loads, typically consisting of a drum or spool around which a rope, cable, or chain...