Glossary Archive

The Ready to Recieve signal shows the sender that the recipient is ready to receive a message. This shape is displayed once the sender has used the Attention (Flag Semaphore) signal before starting the communication.

A reef is a submerged ridge of rock, coral, or sand near the surface of oceans or seas. It can be made up of living organisms like coral or formed by the accumulation of sand or rocks. Reefs are important ecosystems that provide habitat for various marine life and help protect coastlines from erosion.

The act of reducing the area of a sail to decrease wind exposure and maintain control in strong winds. Reefing is an essential technique in sailing that allows sailors to adapt to changing wind conditions. When the wind becomes too strong, a full sail can overpower the boat, making it difficult to control and potentially...

A curved metal fitting on a boom or mast used to secure the reefing cringle of a sail when reducing its area in strong winds. A reefing hook is an essential piece of hardware found on many sailing vessels, particularly those with traditional slab reefing systems. Typically made of stainless steel or another corrosion-resistant material,...

Ropes or cords used to reduce the sail area by securing a portion of the sail to the boom or mast, thereby making the vessel more manageable in strong winds. Reefing lines are a critical component of a sailboat's rigging system, designed to facilitate the process of reefing, which involves reducing the size of a...

When the sender is not actively sending messages, both flags are held by their side. The same shape is also used for Space (Flag Semaphore) & Ready (Flag Semaphore).

A ship that, due to the nature of its work, is unable to keep out of the way of other vessels as required by the International Regulations for Preventing Collisions at Sea (COLREGs). A vessel classified as "Restricted in Ability to Manoeuvre" (RAM) is one that cannot deviate from its course or alter its movements...

Conditions in which a vessel's ability to see is significantly reduced due to environmental factors such as fog, heavy rain, snow, or mist. Restricted visibility is a critical term in maritime navigation, as it describes situations where a vessel's crew cannot see as far as they normally would, making it difficult to navigate safely. This...

A line on the surface of the earth that cuts all meridians at the same angle.  On a standard Mercator chart the rhumb line appears as a straight line

A loop of rope that crosses over itself on a winch drum or cleat, often causing friction or jamming. A riding turn is a term commonly used in the context of rope handling aboard vessels, particularly when dealing with winches, cleats, or other devices used to secure or manage lines. It occurs when a rope...