buttocks(noun) noun1. the fleshy part of the human body that you sit on- he deserves a good kick in the buttSimilar word(s): backside, behind, bottom, bum, buns, butt, can, derriere, fanny, fundament, hindquarters, keister, nates, posterior, prat, rear, rump, seat, stern, tail, tushDefinition categories: body