Source : Webster's Revised Unabridged Dictionary (1913)

Clapper \Clap"per\, n.
   1. A person who claps.

   2. That which strikes or claps, as the tongue of a bell, or
      the piece of wood that strikes a mill hopper, etc. See
      Illust. of {Bell}.

   {Clapper rail} (Zo["o]l.), an Americam species of rail
      ({Rallus scepitans}).