Fonzie thumb Share definition Flag When someone slips a thumb into your butthole by accident or on purpose causing you to yell, "AYE!". "Aye!" Get your thumb away from my asshole. You and your damn Fonzie thumb. Fonzie thumb by HA_13 November 17, 2015 0 0 Get merch Get the Fonzie thumb mug. Buy Now — $32.95 See more merch