'buttocks' definitions:

Definition of 'buttocks'

From: WordNet
noun
The fleshy part of the human body that you sit on; "he deserves a good kick in the butt"; "are you going to sit on your fanny and do nothing?" [syn: 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]

Definition of 'buttocks'

From: GCIDE
  • buttocks \but"tocks\ n. pl. the fleshy part of the human body at the back of the hip, on which a person sits.
  • Syn: 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. [WordNet 1.5]