horn (hôrn)

1. One of the hard, usually permanent structures projecting from the head of certain mammals, such as cattle, consisting of a bony core covered with a sheath of keratinous material.
2. A hard protuberance that is similar to or suggestive of a horn.
3. The hard, smooth keratinous material forming the outer covering of animal horns.
4. Any of the major subdivisions of the lateral ventricle in the cerebral hemisphere of the brain: the frontal horn, occipital horn, and temporal horn. Also called cornu.