n. 1. the fleshy part of the human body at the back of the hip, on which a person sits; teh buttocks.
Syn. -- buttocks, arse, butt, backside, bum, buns, can, fundament, hind end, keister, posterior, prat, rear, rear end, rump, stern, seat, tail, tail end, tooshie, tush, bottom, behind, derriere, fanny, ass. [ WordNet 1.5 ]

2. the part of a quadruped that corresponds to the human buttocks.
Syn. -- croup, croupe, rump. [ WordNet 1.5 ]