1) Group masturbation, usually males, sitting or standing in a circle jerking themselves or each other off.
2) A fraternity initiation ritual or hazing whereby the lights are turned off. The plege or pledges are told it's a circle jerk. The actives pound their fists together in the darkness simulating the sound of jerking off. The lights are then turned on suddenly and the pledge or pledges are the only ones in the circle with their dicks out.
3) A useless discussion or meeting involving mental masturbation whereby the egotistical, boring participants try to demonstrate they're the smartest persons in the room.
The pledges learned humility from the initiation circle jerk.
Trucker CB (citizens band) slang for the position of a vehicle in a line of vehicles that is neither at the front or rear of the line. A vehicle in the "rocking chair" is supposedly protected from law enforcement or smokey because it can receive warning by CB radio from those vehicles ahead and behind about oncoming (or overtaking) patrol cars, speed traps, etc.
I was in the rocking chair and escaped a speeding ticket because the lead trucker warned me of a patrolman with a radar gun (Kojak with a Kodak).