Source : Webster's Revised Unabridged Dictionary (1913)

Guillemot \Guil"le*mot`\, n. [F.] (Zo["o]l.)
   One of several northern sea birds, allied to the auks. They
   have short legs, placed far back, and are expert divers and
   swimmers.

   Note: The common guillemots, or murres, belong to the genus
         {Uria} (as {U. troile}); the black or foolish guillemot
         ({Cepphus grylle}, formerly {Uria grylle}), is called
         also {sea pigeon} and {eligny}. See {Murre}.

Source : WordNet®

guillemot
     n : small black or brown speckled auks of northern seas