1. A mark in the skin or flesh of an animal, made by a wound or ulcer, and remaining after the wound or ulcer has healed; a cicatrix; a mark left by a previous injury; a blemish; a disfigurement.
2. A lasting effect left on someone's mind by a personal misfortune or unpleasant experience which may leave a person with an emotional scar.
3. In botany, a mark left on a stem or branch by the falling of a leaf, a leaflet, or a frond, or upon a seed by the separation of its support.
4. A mark remaining after the healing of a wound or other morbid process; also called a cicatrix.
5. Any of various manifestations of an earlier damage or event.
6. Etymology: from Old French escare, "scab", from Late Latin eschara, from Greek eskhara, "scab formed after a burn"; literally, "hearth, fireplace"; especially, "a scar caused by burning"; which is of uncertain etymology.

Its use in English may have come from a sense probably influenced by the Middle English skar (A.D. 1390), "crack, cut, incision"; and possibly from Old Norse skarð.