In trouble or an awkward position, out of luck, as in His check bounced, leaving Jim behind the eight ball with his landlord. The term comes from pocket billiards or pool, where in certain games if the number eight ball is between the “cue ball” and “object ball” the player cannot make a straight shot. [Colloquial; c. 1920]

A term, referring to the game of pool, meaning in an unfavorable or uncomfortable position: “After his unkind remarks were repeated to the boss, Gary really ended up behind the eight ball.”