buttoosh Share definition Flag Your arse , ass ,backside , bottom or rear end . Defined by my 6 yr old lad. Not a word used at school by his mates, he made it himself and I'm very proud of him. I kicked him in the buttoosh and he cried. buttoosh by Simpleton December 29, 2014 0 0 Get merch Get the buttoosh mug. Buy Now — $32.95 See more merch