Definition of metazoans:
(n) :
(zoology) Any animal that is multicellular.
(adj) :
Having to do with animals that are multicellular.
(adj) :
Having to do with animals that develop from an embryo with three tissue layers.
(n) :
(zoology, obsolete) Any animal that undergoes development from an embryo stage with two or three tissue layers, namely the ectoderm, endoderm, and sometimes mesoderm.