A gay man who attends circuit parties on a regular basis. It is usually a very expensive endeavor, since tickets to the parties are generally around $100 per event, and circuit parties usually take place on three to five consecutive nights in the the same city. The term often has a negative connotation.
He's getting to be such a circuit boy! He's been to three circuit parties this month! I don't know where he gets the money, or how he holds down his job -- he can't go into work sketchy every Monday!