Fatty Addy Share definition Flag Slang for Adderall, a prescription drug used to treat weight problems and ADHD "Yo man, I gotta study all night for that huge history final. Can you hook me up with a fatty addy?" Fatty Addy by james diamond March 23, 2006 0 0 Get merch Get the Fatty Addy mug. Buy Now — $32.95 See more merch