- Any of various animals, such as tapeworms or trematodes, that inhabit the internal organs or tissues of other animals, usually as parasites.
- One of the <em>Entozoa</em>; an internal parasite; an entozoan.
- One of the Entozoa.
- Any of various microscopic <xref>parasitic</xref> worms previously classified together under the grouping Entozoa.
- any of various parasites that live in the internal organs of animals (especially intestinal worms)