Also known as the penis. There is no muscle in the penis, the penis is erect by a massive rush of blood. Therefore another nickname for the penis is the Main Vain.
Don't use the brain, use the Main Vain!
by Butcher Jadali August 27, 2009
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1. The act of releasing urine from your penis.

2. The act of releasing semen from your penis
I drained the main vain all over her.

Well, time to drain the main vain
by Nttm May 12, 2010
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as in you need to go urinate(av a piss).
B: aw ive drunk too much. coming to drain the main vain?
C: yer sure...
by gareth matthews January 28, 2007
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Snorting a white powdery substance off a fully torqued penis
did you hear about Leslie!? last weekend she was railing the main vain on a cruise ship and now shes married to a 65 year old millionaire.
by Jerry Himself August 2, 2017
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