Any Scottish person who is especially hot. Usually applies to men. Examples are John Barrowman, Sean Connery, and most popularly, David Tennant. Can be used as an exclamation as well as a noun/label. More commonly used in the US than in Britain, confusingly.
Person a) Did you see David Tennant
on Doctor Who
Person b) That man is a hot scot! Phwoar
person a) Man, I just did all my homework and went cliff diving IN THE SAME DAY.
person b) HOT SCOT!