Horn

1. a hard permanent outgrowth, often curved and pointed, found in pairs on the heads of cattle, sheep, goats, giraffes, etc. and consisting of a core of bone encased in keratinized skin.
2. the substance of which horns are composed.

   powdered rhino horn

3. a horn-shaped projection or object.
4. a wind instrument, conical in shape or wound into a spiral, originally made from an animal horn (now typically brass) and played by lip vibration.
5. a device sounding a warning or other signal.

   a car horn

1. (of an animal) butt or gore (someone or something) with the horns.
2. be unfaithful to (one's husband or wife).

Old English, of Germanic origin; related to Dutch hoorn and German Horn, from an Indo-European root shared by Latin cornu and Greek keras .