Brown curtains
When a male doesn't wipe his arse properly after pooping . When he parts his bum cheeks you see shit caked in his arse hair aka brown curtains
I ran out of toilet paper while wiping now I have some nasty arse brown curtains
Brown Curtain
A sexual act. When a man is engaged in sex in the doggy position, he inserts his penis into her (or his) anus and fucks them until he cums. Then withdrawing his penis and wiping it on her (or his) new light colored curtains. It usually ends with the other partner freaking the fuck out.
Dude, the bitch cheated on me, so I pulled a Brown Curtain on her last night.