any of various parasitic nematode worms, esp. a species (Enterobius vermicularis) often found in the human rectum and large intestine, esp. in children
See pinworm in American Heritage Dictionary 4
Any of various small nematode worms of the family Oxyuridae that are parasitic on horses, rabbits, and other mammals, especially Enterobius vermicularis, a species that infests the human intestines and rectum. Also called threadworm.