acoelomate
/eɪˈsiːlə(ʊ)meɪt/(also acelomate) Zoology
adjective
Of an animal or animal phylum: having no coelom or principal body cavity; not coelomate.
noun
An acoelomate animal.
Origin
Late 19th century; earliest use found in Francis Bell (1855–1924). From a- + coelomate.