What is Karl Mark?
1.
A Shit/Poop mark that appears on your boxers or underwear. It is usually a long streak of feces that runs along your bumline and may look like Karl from the simpsons.
Mom - "OH MY GOD! THIS IS THE FIFTH PAIR OF UNDERWEAR YOU'VE RUINED THIS WEEK. CLEAN YOUR ASS OR YOU'LL HAVE KARL MARKS ALL YOUR LIFE. WHAT GIRL WOULD WANT TO DATE YOU AFTER KNOWING ABOUT THAT?
Fat Kid - "Sorry Ma, its just that when I sit for long periods of time, my ass becomes sweaty and produces crap. I especially smell during Gym! I have to occasionally wipe my ass like five times a day because my ass cheeks rub against each other."
See