downstairs brain Share definition Flag A man's sexual organs, as opposed to his usual so-called-brain, the upstairs brain. Mike wasn't digging Jen, but three beers later he was thinking with his downstairs brain. Now he has herpes. downstairs brain by MWazza April 17, 2009 0 0 Get merch Get the downstairs brain mug. Buy Now — $32.95 See more merch
