from
The Collaborative International Dictionary of English v.0.48
Centerboard \Cen"ter*board`\, Centreboard \Cen"tre*board\,
(s[e^]n"t[~e]r*b[=o]rd`), n. (Naut.)
A retractable or sliding keel used on sailboats, 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 drifting to leeward when the vessel is beating to
windward. It is used in vessels of all sizes along the coast
of the United States
Syn: centreboard, drop keel, sliding keel.
[1913 Webster]