The Collaborative International Dictionary of English v.0.48:

Mesozoa \Mes`o*zo"a\, n. pl. [NL. See Mesozoic.] (Zool.)
   A group of very lowly organized, wormlike parasites,
   including the Dicyemata. They are found in cephalopods. See
   Dicyemata.
   [1913 Webster]