to fuck something up so bad that only the word "coop" is eligible to describe the magnitude of how bad that person fucked up.
Tony: "Dude how could you possibly pass up that 3-some??"
Cooper: "I didn't pass it up, dude."
Tony: "Then, what happened?"
Cooper: "I got too excited and shit in my pants."
Tony: "WOW. You really cooped it."
Cooper: "I know. I'm a fag."