The Collaborative International Dictionary of English v.0.48:

Gaper \Gap"er\ (g[=a]p"[~e]r), n.
   1. One who gapes.
      [1913 Webster]

   2. (Zool.)
      (a) A European fish. See 4th Comber.
      (b) A large edible clam (Schizoth[ae]rus Nuttalli), of
          the Pacific coast; -- called also gaper clam.
      (c) An East Indian bird of the genus Cymbirhynchus,
          related to the broadbills.
          [1913 Webster]