Source : Webster's Revised Unabridged Dictionary (1913)

Horsehair \Horse"hair`\, n.
   A hair of a horse, especially one from the mane or tail; the
   hairs of the mane or tail taken collectively; a fabric or
   tuft made of such hairs.

   {Horsehair worm} (Zo["o]l.), the hair worm or gordius.