threadworm (pinworm) Small roundworm of the phylum Aschelminthes. It is most common in moist tropical regions and resembles a short length of hair or thread. It may inhabit the intestines of human beings and other animals, but can live and breed freely in soil. Species Oxyurus vermicularis.

threadworm (pinworm) (thred-werm) n. a parasitic nematode worm of the genus Enterobius (Oxyuris), which lives in the upper part of the human large intestine. Threadworms cause enterobiasis, a disease common in children throughout the world.

thread·worm / ˈ[unvoicedth]redˌwərm/ • n. a very slender parasitic nematode worm, esp. a pinworm.