Threadworms

• Eelworms
• Unsegmented worms roundworms

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Nematoidea \Nem`a*toi"de*a\, prop. n. pl. [NL., fr. Gr. nh^ma, nh`matos, thread + -oid.] (Zo["o]l.) A phylum of worms, having a long, round, and generally smooth body; the roundworms. Called also Nematodea , and more commonly Nematoda . Formerly, it was ...

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
a class of worms, Modern Latin compound of nemat- "thread" (from Greek nema , genitive nematos "thread," from stem of nein "to spin;" see needle (n.)) + -odes "like, of the nature of" (see -oid ).