NOUN: A cart barrier is when you place your cart (aka ball sack) in a woman mouths and the woman then proceeds to craftfully and carefully use her tongue to create a barrier between the two testicles in her mouth, creating a barrier. Commonly practiced in the midwestern portion of United States.
Part of this process is called "breaking the cart barrier". In order to achieve the breaking of the cart barrier the following must happen. While the ball sack is still in the woman's mouth, the woman must use both free hands to stimulate the penis AND the prostate. Upon climax the male should release the contents of his cart (semen) onto the woman's hair. Once this is all accomplished the man can declare that he has broken the cart barrier.
"Guys so get this. Good News. My girlfriend and I finally broke the cart barrier today. Her hair was such a mess afterwords."
In Call Of Duty Zombies, when you're at a barrier shooting zombies and knifing them, and the zombies hit you through the barrier and you get downed. Often happens on a very low round and is a great source of embarrassment.
Player 1: *knifes zombie*
Zombie: *hits player twice and downs him*
Game: "GAME OVER. You survived 1 round"
Onlooker: "Lol, you're so bad at call of duty zombies, you can't get past round 1."
Player 1: "It's not my fucking fault, I got barrier raped"