Source : Webster's Revised Unabridged Dictionary (1913)

Beluga \Be*lu"ga\ (b[-e]*l[=u]"g[.a]), n. [Russ. bieluga a sort
   of large sturgeon, prop. white fish, fr. bieluii white.]
   (Zo["o]l.)
   A cetacean allied to the dolphins.

   Note: The northern beluga ({Delphinapterus catodon}) is the
         white whale and white fish of the whalers. It grows to
         be from twelve to eighteen feet long.

Source : WordNet®

beluga
     n 1: valuable source of caviar and isinglass; found in Black and
          Caspian seas [syn: {hausen}, {white sturgeon}, {Acipenser
          huso}]
     2: small northern whale that is white when adult [syn: {white
        whale}, {Delphinapterus leucas}]