anal leakage resulting in a shit stain on your pants, common among old bastards and sluts with loose back doors.
1:Dude you need to talk to your mom about that stainus. 2: I can smell that stainus from over here.
by Rocco Cocko III May 08, 2010
1 more definition
Top Definition
a stained anus, kinda browner than you think it should be...maybe even a dingle-berry or two present. Rhymes with anus.
Biff: Hey Blaine...that chick I banged last was awesome. But, when she bent over and pulled her panties off, I saw her stainus! It was rotten. But, I did her anyways.
Blaine: Did your tool smell like ass?
by saintsfanmd July 10, 2008

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