One's plan or scheme has been discovered and/or thwarted; one's game, trick, or deception is at an end. A variant of the much more common phrase "the jig is up." Your jig is up, Senator Marten! Your tax evasion has been found out, and the police are here to escort you to prison. We were going to play a practical joke on David, but when he noticed our car parked out front, I knew that our jig was up.