Wiktionary
vb. (context mildly taboo slang chiefly British NZ English) To ruin (something) unintentionally; to screw up, mess up or fuck up.
WordNet
Usage examples of "cock up".
There's an Arab here likes to fuck woman in company - one cock up your arse, another in your cunt, maybe a third in your mouth.
The hand around my cock forced it out straight, and I felt the Master's right hand surrounding the tip, the cream slipping around the tortured flesh and then the hand tightening and riding the cock up and down in rhythm with the thrusts into my backside.
The girl has begun to play with herself with one hand and she's using the other to shake Ernest's cock up.
What a delight it will be for me to tongue your cunny while you have a cock up your bottom.
The groans became breathless cries and, after not even a dozen plunges of the cock up into the steaming slush, the whipped nude disintegrated hysterically.
Right now she was more concerned with keeping herself from jumping his broad body and stuffing his cock up her pussy.
No fragile princess could take a cock up her ass like that and beg for more.
Play with it while I push every hard inch of my cock up your tight pussy.
Rubbing his cock up and down her shallow groove, he pressed hard enough to part her labia, hard enough to slide the tip of his bulbous head through her drenched folds.