The Collaborative International Dictionary of English v.0.48:

Bowhead \Bow"head`\, n. (Zool.)
   The great Arctic or Greenland whale. (Bal[ae]na
   mysticetus). See Baleen, and Whale.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bowhead
    n 1: large-mouthed Arctic whale [syn: bowhead, bowhead
         whale, Greenland whale, Balaena mysticetus]