1. A scratch or abrasion (process of wearing away by friction) of the skin.
2. The act of excoriating or flaying, or state of being excoriated, or stripped of the skin; abrasion.
3. A superficial loss of dermal substance, as may be produced on the skin by scratching.
4. Abrasion of the epidermis or of the coating of any organ by trauma, chemicals, burns, or other causes.

1. A self-induced skin lesion, inflicted by the fingernails or by other physical actions.
2. A self-inflicted excoriation, usually on the face, back, or shoulders of a subject when under stress.