Source : Webster's Revised Unabridged Dictionary (1913)

Percolator \Per"co*la`tor\, n.
   1. A kind of coffee pot in which the heated water is caused
      to filter through the coffee and thus extract its essence.

   2. (Pharmacy) An apparatus for producing an extract from a
      drug by percolation.

Percolator \Per"co*la`tor\, n.
   One who, or that which, filters. ``[Tissues] act as
   percolators.'' --Henfrey.

Source : WordNet®

percolator
     n : a coffeepot in which boiling water ascends through a central
         tube and filters back down through a basket of ground
         coffee beans