When you have anal sex and then wipe the crap on your partner's upper lip giving them a Hitler.

A Dirty Sanchez is a sexual situation where a man is laying some pipe doggy-style, and while in the midst of sex he inserts his finger in the womans starfish and then smears his finger across her upper lip, giving her a thin shit moustache. This is the Dirty Sanchez.

a dirty sanchez is when you have anal sex and then smear the remaining feces onto your partners upper lip, like a mustache.

The sexual act of a man inserting his finger into a woman's anal cavity