A sexual act in which you are nailing a chick missionary style without a condom, and just as you are about to cum you scream, "I'm CUMMING!" Just as you blast your wad, you elbow drop the girl in the face, knocking her out cold. You then run like hell.
"Dude, remember that chick who was drunk at the party last night?"
"Yeah, I remember her. Did you nail her?"
"Hell yes, man, I gave her the Rock 'em Sock 'em! She won't remember who knocked her up!"