The Collaborative International Dictionary of English v.0.48:

Spencer \Spen"cer\, n. [OF. despensier. See Spence, and cf.
   Dispenser.]
   One who has the care of the spence, or buttery. [Obs.]
   --Promptorium Parvulorum.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spencer \Spen"cer\, n. [From the third Earl Spencer, who first
   wore it, or brought it into fashion.]
   A short jacket worn by men and by women. --Ld. Lutton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

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]

The Collaborative International Dictionary of English v.0.48:

Trysail \Try"sail\, n. (Naut.)
   A fore-and-aft sail, bent to a gaff, and hoisted on a lower
   mast or on a small mast, called the trysail mast, close abaft
   a lower mast; -- used chiefly as a storm sail. Called also
   spencer. --Totten.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Spencer
    n 1: English philosopher and sociologist who applied the theory
         of natural selection to human societies (1820-1903) [syn:
         Spencer, Herbert Spencer]