Definition of protocoelomate in US English:

protocoelomate

noun

Zoology
rare
  • Originally: (A. S. Hyatt's name for) a member of a grade of primitive multicellular animals characterized by a simple central cavity with branching sacs (not now considered coelomic), comprising most or all of the sponges. Now: a metazoan animal considered to represent or resemble a common ancestor of coelomate phyla.

Origin

Late 19th century. From proto- + coelomate. Compare scientific Latin protocoelomata.

Pronunciation

protocoelomate

/ˌprəʊtə(ʊ)ˈsiːlə(ʊ)meɪt/