anal leakage resulting in a shit stain on your pants, common among old bastards and sluts with loose back doors.
by Rocco Cocko III May 8, 2010
Get the stainus mug.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?
Blaine: Did your tool smell like ass?
by saintsfanmd June 23, 2008
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