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.