any of a phylum (Nemata) of worms, often parasites of animals and plants, with long, cylindrical, unsegmented bodies and a heavy cuticle, as the hookworm or pinworm; roundworm
See nematode in American Heritage Dictionary 4
(nĕmˈə-tōdˌ, nēˈmə-)
noun
Any of several worms of the phylum Nematoda, having unsegmented, cylindrical bodies, often narrowing at each end, and including parasitic forms such as the hookworm and pinworm. Also called roundworm.