The term 'dirty sanchez' originated in the porn industry, particularly films involving ass-to-mouth (atm) action. It describes the (originally unintentional, i.e. blooper ) act of leaving a shit moustache on a partner's face by taking your cock out of her ass and putting it in her mouth without wiping it off first. The result is that as the dick is thrust between the lips, shit is scraped off and comes to rest on her upper lip in a moustache configuration.Anyone who thinks it involves the deliberate wiping of shit with fingers on a partner's face is a know-nothing fucktard.