It stands for "Ultimate Comfort Zone"!
It is when you are laying around anytime and you happen to find that zone, that a man may only find once in his life but you may get lucky and find that zone everyday. It is a feeling that you have never felt but when it happens you will know. You just lay and find a position you know can be no more comfortable and you never want to move.
Dude, I cant wait to get home and put on my laying clothes and find my U.C.Z.