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Webster 1913 Edition

Noun.

(Zool.)

Any worm belonging to the

Platyhelminthes

; also, sometimes applied to the planarians.

flatworm ‎(plural flatworms)

Any of very many parasitic or free-living worms, of the phylum Platyhelminthes, having a flattened body with no skeleton or body cavity.

worm of Platyhelminthes