Nematoidea

prop. n. pl.
  1. A phylum of worms, having a long, round, and generally smooth body; the roundworms. Called also Nematodea, and more commonly Nematoda. Formerly, it was classed as a taxonomic order.

The trichina, stomach worm, and pinworm of man belong to this group. See also Vinegar eel, under Vinegar, and Gapeworm.