Source : Webster's Revised Unabridged Dictionary (1913)

Humpback \Hump"back`\, n. [Cf. {Hunchback}.]
   1. A crooked back; a humped back. --Tatler.

   2. A humpbacked person; a hunchback.

   3. (Zo["o]l.)
      (a) Any whale of the genus {Megaptera}, characterized by a
          hump or bunch on the back. Several species are known.
          The most common ones in the North Atlantic are
          {Megaptera longimana} of Europe, and {M. osphyia} of
          America; that of the California coasts is {M.
          versabilis}.
      (b) A small salmon ({Oncorhynchus gorbuscha}), of the
          northwest coast of America.

Source : WordNet®

humpback
     n 1: an abnormal backward curve to the vertebral column [syn: {kyphosis},
           {hunchback}]
     2: a person whose back is hunched because of abnormal curvature
        of the upper spine [syn: {hunchback}, {crookback}]
     3: large whalebone whale with long flippers noted for arching
        or humping its back as it dives [syn: {humpback whale}, {Megaptera
        novaeangliae}]