the word of the day is keister...

Dictionary.com/keister keister

n : the fleshy part of the human body that you sit on [syn: buttocks, arse, butt, backside, bum, buns, can, fundament, hindquarters, hind end, posterior, prat, rear, rear end, rump, stern, seat, tail, tail end, tooshie, tush, bottom, behind, derriere, fanny, ass]