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Referring to the exchanging of bodily fluids between two guys through the course of anal sex.
One may say this in a joking way to ones chums to gain a chance of laughter, but has really got, what the youth of today call "issues" and should stop being so "batty"
Mike says to Patric
"mate forget about going to The Hart, lets go to that gay bar - The Birdcage. After all, one up the bum no harm done." This is when Patric would probably knock the shit out of Mike, grab a beer and go to The Hart.
by Mike June 06, 2003
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