any of a phylum (Bryozoa) of minute water animals that form branching, mosslike colonies and reproduce by budding
See bryozoan in American Heritage Dictionary 4
(brīˌə-zōˈən)
noun
Any of various small aquatic animals of the phylum Bryozoa that reproduce by budding and form mosslike or branching colonies permanently attached to stones or seaweed. Also called moss animal, polyzoan.