'Spencer mast' definitions:

Definition of 'Spencer mast'

From: GCIDE

Spencer \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 [1802]. [1913 Webster]
Spencer mast, a small mast just abaft the foremast or mainmast, for hoisting the spencer. --R. H. Dana, Jr. [1913 Webster]