\Cen"ter*board`\, Centreboard \Cen"tre*board\,, n.
(Naut.)
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 States