Butter Swamp
Butter Swamp is the post-sex area of a guy's balls and thighs where all of the girl's natural vaginal juices dripped down during sex, especially if she was on top most of the time. If the guy is top most of the time, it's the girls thighs and butt crack where all of the vaginal juices and cum drip down.
We were late to the party because he had to shower all of the butter swamp off before we left. or He dipped his finger in her butter swamp and traced it around her nipple.