The inability to come from a blow-job given by a girl, because you mind is thinking about other guys. It's a combination of the words Regress and Cock.
Guy#1: Hey Bro, I saw you leaving with a hot chick last night...
Guy#2: Yeah, she was hot but the night ended in a gresock.
When your having sex with a significant other. when your cat comes in unannounced. and you start having sex with your cat and make your significant other sleep on the couch.