The act of engaging in intercourse with someone who has recently been divorced/widowed/broken up. A combination of rebound and one night stand, the ideal time window for humpfort is anywhere from the day after to a week after, when he/she is still emotional, and possibly going through sex withdrawal. The emotion clouds the mind, while the withdrawal cravings gives them drive; this combination means an easy score for practitioners of humpfort. If performed correctly, humpfort has all of the benefits of both rebounds and one night stands without the consequences. And if anything does go wrong, just blame the person you just slept with.
Jake: "Hans, you bastard, you slept with my ex -- not even an hour after we broke up!"
Hans: "Bra, ease up. It was humpfort, she totally was like all up on me before I could do anything. She's a whore, a complete scumbag and all the problems of the world can be blamed on her. Good thing you broke up with her."
Jake: "True that, Hans. Let's go listen to some generic rap-rock music in our rice burners."