A fork of Rural Dictionary
"Hot Karl" is a slang term for sex which involves feces. Such variations of a "Hot Karl" are having a bowel movement in your partner's mouth, the female partner giving the male partner fellatio after he has had anal sex with her, or when a parter has a bowel movement on the other partners stomach (usually, the partner getting boweled on has Saran Wrap on his/her stomach).
My wife and I experimented with the Hot Karl, wow do I love the taste of my woman's shit.