The Collaborative International Dictionary of English v.0.48:

Whale \Whale\, n. [OE. whal, AS. hw[ae]l; akin to D. walvisch,
   G. wal, walfisch, OHG. wal, Icel. hvalr, Dan. & Sw. hval,
   hvalfisk. Cf. Narwhal, Walrus.] (Zool.)
   Any aquatic mammal of the order Cetacea, especially any one
   of the large species, some of which become nearly one hundred
   feet long. Whales are hunted chiefly for their oil and
   baleen, or whalebone.
   [1913 Webster]

   Note: The existing whales are divided into two groups: the
         toothed whales (Odontocete), including those that
         have teeth, as the cachalot, or sperm whale (see Sperm
         whale); and the baleen, or whalebone, whales
         (Mysticete), comprising those that are destitute of
         teeth, but have plates of baleen hanging from the upper
         jaw, as the right whales. The most important species of
         whalebone whales are the bowhead, or Greenland, whale
         (see Illust. of Right whale), the Biscay whale, the
         Antarctic whale, the gray whale (see under Gray), the
         humpback, the finback, and the rorqual.
         [1913 Webster]

   Whale bird. (Zool.)
   (a) Any one of several species of large Antarctic petrels
       which follow whaling vessels, to feed on the blubber and
       floating oil; especially, Prion turtur (called also
       blue petrel), and Pseudoprion desolatus.
   (b) The turnstone; -- so called because it lives on the
       carcasses of whales. [Canada]

   Whale fin (Com.), whalebone. --Simmonds.

   Whale fishery, the fishing for, or occupation of taking,
      whales.

   Whale louse (Zool.), any one of several species of degraded
      amphipod crustaceans belonging to the genus Cyamus,
      especially Cyamus ceti. They are parasitic on various
      cetaceans.

   Whale's bone, ivory. [Obs.]

   Whale shark. (Zool.)
   (a) The basking, or liver, shark.
   (b) A very large harmless shark (Rhinodon typicus) native
       of the Indian Ocean. It sometimes becomes sixty feet
       long.

   Whale shot, the name formerly given to spermaceti.

   Whale's tongue (Zool.), a balanoglossus.
      [1913 Webster]

WordNet (r) 3.0 (2006):

whale louse
    n 1: amphipod crustacean parasitic on cetaceans