A distinguishing mark, usually a reddy patch of skin or an unusual mole, that a person has from birth. A significant minority of the population has a birthmark of some sort.

Famous birthmarks:
- Mikhail Gorbachev had a large red birthmark on his head, very visible once he went bald. (My parents named their cat Gorby because of his unusual head markings..)
- A boy in Lord of the Flies who is identified only as the boy with the mulberry (coloured) mark, who mysteriously disappears without a trace after the first confusing night the boys spend on the island.
- more?