mesozoan[mes′ə zō′ən, mez′-]
any of a phylum (Mesozoa) of small, multicellular, wormlike organisms characterized by a very simple, ciliated body with only a mouth, body cavity, and anus: it is a parasite in various marine invertebrates
Any of various small wormlike animals that are parasites of marine invertebrates and have an inner layer of one or more cells surrounded by an outer layer of ciliated cells.
Origin of mesozoanFrom New Latin Mesozōa, former phylum name : meso– (because the animals were considered to be intermediate between the protozoans and the metazoans in structure) + -zōa, pl. of -zōon, animal; see –zoon.