Source : Webster's Revised Unabridged Dictionary (1913)

Bluefin \Blue"fin`\, n. (Zo["o]l.)
   A species of whitefish ({Coregonus nigripinnis}) found in
   Lake Michigan.

Source : WordNet®

bluefin
     n 1: flesh of very large tuna [syn: {bluefin tuna}]
     2: largest tuna; to 1500 pounds; of mostly temperate seas: feed
        in polar regions but breed in tropics [syn: {bluefin tuna},
         {horse mackerel}, {Thunnus thynnus}]