Source : Webster's Revised Unabridged Dictionary (1913)

Clapper \Clap"per\, n. [F. clapier.]
   A rabbit burrow. [Obs.]

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}).

Source : WordNet®

clapper
     n 1: someone who applauds [syn: {applauder}]
     2: a mobile mass of muscular tissue covered with mucous
        membrane and located in the oral cavity [syn: {tongue}, {lingua},
         {glossa}]
     3: metal striker that hangs inside a bell and makes a sound by
        hitting the side [syn: {tongue}]