Source : Webster's Revised Unabridged Dictionary (1913)

Polypi \Pol"y*pi\, n. pl. [NL.] (Zo["o]l.)
   The Anthozoa.

Polypus \Pol"y*pus\, n.; pl. E. {Polypuses}, L. {Polypi}. [L.
   See {Polyp}.]
   1. (Zo["o]l.) Same as {Polyp}.

Source : WordNet®

polypus
     n : a small vascular growth on the surface of a mucous membrane
         [syn: {polyp}]
     [also: {polypi} (pl)]

polypi
     See {polypus}