Dictionary.net

A pointed process.

.A conical, hard, epidermous projection, which grows on the heads of certain animals, serving them as a weapon of offence and defence. Anatomists have given this name to parts of the human body, which have nearly the same shape as the horns of animals.

L. for Horn.

PI. cornua.

A horn-shaped process or appendage.

A horn-shaped extension of a cavity, e. g., those of the lateral ventricle of the brain and those of the cavity of the uterus.