1. One of the hard, usually permanent structures projecting from the head of certain mammals, such as cattle, sheep, goats, or antelopes, consisting of a bony core covered with a sheath of keratinous material.
2. A hard protuberance, such as an antler or a projection on the head of a giraffe or rhinoceros, that is similar to or suggestive of a horn.
3. a. The hard, smooth keratinous material forming the outer covering of the horns of cattle or related animals. b. A natural or synthetic substance resembling this material.
4. A container, such as a powder horn, made from a horn.
5. Something having the shape of a horn, especially: a. A horn of plenty; a cornucopia. b. Either of the ends of a new moon. c. The point of an anvil. d. The pommel of a saddle. e. An ear trumpet. f. A device for projecting sound waves, as in a loudspeaker. g. A hollow, metallic electromagnetic transmission antenna with a circular or rectangular cross section.
6. Abbr. h., H. Music. a. A wind instrument made of an animal horn. b. A brass wind instrument, such as a trombone or tuba. c. A French horn. d. A wind instrument, such as a trumpet or saxophone, used in a jazz band.
7. a. A usually electrical signaling device that produces a loud, resonant sound: an automobile horn. b. Any of various noisemakers operated by blowing or by squeezing a hollow rubber ball.
8. Slang. A telephone.