A Shitler is when you give a Rimjob to your lover and they have a dirty ass so you get a brown patch on your top lip that looks like a Hitler mustache
Joel: Hey Remi I heard you hooked up with Nadia last night
Remi: Yeah bro I gave her a Rimjob and when I when to the bathroom later I realized she gave me a Shitler
Joel: Next time make sure to wipe her ass before you go in there