Spen′cer.
(Nautical.) A four-cornered foreand-aft sail, whose head is extended by a gaff and its foot usually by a sheet. Its position is abaft the fore or the main mast, and it is frequently bent to an auxiliary spar, called the spencer-mast. It is a trysail to the fore or main mast, and differs from a spanker or driver in position. The latter belong to the mizzen.