Source : Webster's Revised Unabridged Dictionary (1913)

Poppet \Pop"pet\, n.
   1. See {Puppet}.

   2. (Naut.) One of certain upright timbers on the bilge ways,
      used to support a vessel in launching. --Totten.

   3. (Mach.) An upright support or guide fastened at the bottom
      only.

   {Poppet head}, {Puppet head}. See {Headstock}
      (a) .

Source : WordNet®

poppet
     n : a mushroom-shaped valve that rises perpendicular from its
         seat; commonly used in internal-combustion engines [syn:
         {poppet valve}]