The Collaborative International Dictionary of English v.0.48:

Polyzoan \Pol`y*zo"an\, n. (Zool.)
   (a) Any species of Polyzoa; one of the Polyzoa.
   (b) A polyzoon.
       [1913 Webster]

WordNet (r) 3.0 (2006):

polyzoan
    n 1: sessile aquatic animal forming mossy colonies of small
         polyps each having a curved or circular ridge bearing
         tentacles; attach to stones or seaweed and reproduce by
         budding [syn: bryozoan, polyzoan, sea mat, sea
         moss, moss animal]