- (philately, of an issue printed for collectors) Totally fictitious, and often issued on behalf of a non-existent territory or country.
- Forbidden by established rules.
"Moving a pawn backward is an illegal move in chess."
- (chiefly US, sometimes offensive) Being an illegal immigrant; residing in a country illegally.
- Contrary to or forbidden by law, especially criminal law.
"This is illegal, you know!"
- (of a person, sometimes offensive) Being or doing something illegally.
- (colloquial, offensive) An illegal immigrant.
- An illegal resident spy.