An insult used to describe someone who has just done something particularly stupid. It comes from the markings left behind in a womans underwear following some desrciption of vaginal discharge.
Jim: Oh dear, I have appeared to drop my pen.

Bob: God Jim, you're such a twat stain.
by Chris Wynne June 10, 2005
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1. The signature red stain on a girl's undergarments.
2. Anyone and everyone who you do NOT like.
1. The twat-stain on that hooker's panties made my dick about as hard as a banana peel.
2. That twat-stain put chocolate pudding on my nipples while I was furiously masturbating!
by xPedobearz April 11, 2011
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