From WordNet (r) 3.0 (2006):
posterior
adj 1: located at or near or behind a part or near the end of a
structure [ant: anterior]
2: coming at a subsequent time or stage; "without ulterior
argument"; "the mood posterior to" [syn: later(a),
ulterior, posterior]
n 1: 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]
2: a tooth situated at the back of the mouth [syn: back tooth,
posterior]