Centreboard

A board or plate lowered through the hull of a dinghy on the centreline to resist leeway.
Found on http://en.wikipedia.org/wiki/Glossary_of_nautical_terms

Centreboard

A centreboard (UK) or centerboard (US) is a retractable keel which pivots out of a slot in the hull of a sailboat, known as a centreboard trunk (UK) or centerboard case (US). The retractability allows the centreboard to be raised to operate in shallow waters, to move the centre of lateral resistance (offsetting changes to the sailplan that move th...
Found on http://en.wikipedia.org/wiki/Centreboard

Centreboard

• (n.) A movable or sliding keel formed of a broad board or slab of wood or metal which may be raised into a water-tight case amidships, when in shallow water, or may be lowered to increase the area of lateral resistance and prevent leeway when the vessel is beating to windward. It is used in vessels of all sizes along the coast of the United ...
Found on http://thinkexist.com/dictionary/meaning/centreboard/

centreboard

(from the article `keel`) The backbone keel may be supplemented by other keels (see Figure). A `centreboard`—also called a drop keel, or sliding keel—is a retractable keel ...
Found on http://www.britannica.com/eb/a-z/c/45

Centreboard

A board or plate lowered through the hull of a dinghy on the centreline to resist leeway.
Found on http://en.wikipedia.org/wiki/Glossary_of_nautical_terms

Centreboard

A removable keel used to resist leeway.
Found on http://www.translationdirectory.com/glossaries/glossary101.htm

Centreboard

An adjustable fin primarily used to stop the boat moving sideways through the water. Also called daggerboard.
Found on https://www.encyclo.co.uk/local/21233
No exact match found