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; Specifically: a black shiny fabric made of such hairs, used commonly in the 1800's as a covering for stuffed furniture such as chairs and couches. [1913 Webster +PJC] {Horsehair worm} (Zool.), the hair worm or gordius. [1913 Webster]