pa-nay-nay Share definition Flag a slang term for penis-a man's private. Used if you dont want anyone to know what the hell you are talking about! I had sex with this guy and he had a 10 inch long pa-nay-nay pa-nay-nay by Buttsex-is good for your health June 20, 2006 0 0 Get merch Get the pa-nay-nay mug. Buy Now — $32.95 See more merch