birthmark I. \ˈ ̷ ̷ˌ ̷ ̷\noun Etymology:birth (I) + mark 1.: an unusual mark or blemish on the skin at birth : nevus 2.: a distinguishing characteristic or quality < words sang for him, and that is the birthmark of a poet — Dylan Thomas > II. transitive verb : to fix a birthmark on — usually used passively