1. (noun)buttocks, nates, arse, butt, backside, bum, buns, can, fundament, hindquarters, hind end, keister, posterior, prat, rear, rear end, rump, stern, seat, tail, tail end, tooshie, tush, bottom, behind, derriere, fanny, ass the fleshy part of the humanbody that you sit on "he deserves a good kick in the butt"; "are you going to sit on your fanny and do nothing?"