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. [1913 Webster
" The trichina, stomach worm, and pinworm of man belong to this group. See also Vinegar eel, under Vinegar, and Gapeworm."