The Collaborative International Dictionary of English v.0.48:

Bruiser \Bruis"er\, n.
   1. One who, or that which, bruises.
      [1913 Webster]

   2. A boxer; a pugilist; hence, a strong, tough person; --
      often used in the phrase

   big bruiser. --R. Browning.
      [1913 Webster]

            Like a new bruiser on Broughtonic sand,
            Amid the lists our hero takes his stand. --T.
                                                  Warton.
      [1913 Webster]

   3. A concave tool used in grinding lenses or the speculums of
      telescopes. --Knight.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bruiser
    n 1: a large and strong and heavyset man; "he was a bull of a
         man"; "a thick-skinned bruiser ready to give as good as he
         got" [syn: bull, bruiser, strapper, Samson]