Future Cock Block (FCB) is a term used when another male tells a perspective female something that will forever destroy his chances with said woman. Anytime in the future when the man tries to hook up with the woman, he will be denied.
"Dude, I told Jackie you slept with some random fattie. She has a b/f now, but if she's ever available, I think I've future cock blocked you."
by Recipient of a FCB January 29, 2009