A situation in which two individuals, who were once in a relationship but are no longer together, continue to have sex with each other on a regular basis and still act as if they are in a relationship. Alcohol and or drugs enhances this effect to unknown levels.
Observer 1: What's up with Jim and Amanda? I thought they broke up?
Observer 2: They did, but they're caught in the J&J Effect.
Observer 1: Oh, I see. It's a sad sight to see.
Observer 2: Indeed