Word Study
buttocks
CIDE DICTIONARY
buttocks, n. pl.
the fleshy part of the human body at the back of the hip, on which a person sits. [WordNet 1.5]
THESAURUS
buttocks
arse, ass, backside, beam, behind, bottom, breech, bum, butt, can, cheeks, croup, crupper, derriere, duff, fanny, fundament, haunches, heinie, hind end, hinder, hindquarters, keister, nates, posterior, prat, rear, rear end, rump, seat, secretiveness, stem, tail, tail end, tuchis, tush, tushyFor further exploring for "buttocks" in Webster Dictionary Online