A long thin animal with no legs or backbone, which can infest the human body, especially the intestines.
Any member of several groups of soft bodied legless animals, including flatworms, nematode worms, earthworms, and leeches, that were formerly thought to be closely related and classified as a single group (Vermes).
An elongated invertebrate belonging to one of the following phyla: Platyhelminthes (flatworms); Nemathelminthes or Aschelminthes (roundworms or threadworms); Acanthocephala (spiny headed worms); and Annelida (Annulata) (segmented worms).