Source : Webster's Revised Unabridged Dictionary (1913)

Threadworm \Thread"worm`\, n. (Zo["o]l.)
   Any long, slender nematode worm, especially the pinworm and
   filaria.

Source : WordNet®

threadworm
     n : small threadlike worm infesting human intestines and rectum
         especially in children [syn: {pinworm}, {Enterobius
         vermicularis}]