Hairy Uncle Share definition Flag A type of prank where one man drops his pants and underwear in order to fart with his bare ass right in another man's face. The worst April Fool's Day ever was when my brother gave me a Hairy Uncle. Hairy Uncle by Creek Geek May 19, 2012 0 0 Get merch Get the Hairy Uncle mug. Buy Now — $32.95 See more merch