parasitic flatworms having external suckers for attaching to a host

Any parasitic animal organism belonging to the class Trematoda, including flukes.

(Trématodes) Class of acoelomate invertebrate of the phylum Platyhelminthes. A parasitic flatworm whose complex life cycle generally entails two or even three hosts.(Translated from Ramade, F. Dictionnaire encyclopédique de l'écologie et des sciences de l'environnement. Édiscience international, Paris, 1993.)

One of the Trematodea. Also used adjectively.