Dictionary:

acoelomate

  (ə-sē'lə-māt')

An animal that lacks a coelom. Acoelomates, which include the flatworm, fluke, tapeworm, and ribbon worm, exhibit bilateral symmetry and possess one internal space, the digestive cavity.

[New Latin Acoelōmata, group name : A–¹ + Greek koilōma, koilōmat-, cavity; see coelom.]