Spen″cer, n.(Naut.) A fore-and-aft sail, abaft the foremast or the mainmast, hoisted upon a small supplementary mast and set with a gaff and no boom; a trysail carried at the foremast or mainmast; — named after its inventor, Knight Spencer, of England.
Spencer mast, a small mast just abaft the foremast or mainmast, for hoisting the spencer. R. H. Dana, Jr.