The Collaborative International Dictionary of English v.0.48:

Whalebone \Whale"bone`\, n.
   A firm, elastic substance resembling horn, taken from the
   upper jaw of the right whale; baleen. It is used as a
   stiffening in stays, fans, screens, and for various other
   purposes. See Baleen.
   [1913 Webster]

   Note: Whalebone is chiefly obtained from the bowhead, or
         Greenland, whale, the Biscay whale, and the Antarctic,
         or southern, whale. It is prepared for manufacture by
         being softened by boiling, and dyed black.
         [1913 Webster]

WordNet (r) 3.0 (2006):

whalebone
    n 1: a horny material from the upper jaws of certain whales;
         used as the ribs of fans or as stays in corsets [syn:
         whalebone, baleen]