The crusty brown material that gets transferred to the rear of the toilet seat or underwear, resulting from the accumulation of fecal matter at the top of an unclean, too-far-rear-wiping person's ass crack.
I almost sat in the hefty butt smudge that you left on the seat!
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi