[n] excretory opening at the end of the alimentary canal
[n] the fleshy part of the human body that you sit on
anus, arsehole, ass, asshole, backside, behind, bottom, bum, buns, butt, buttocks, can, derriere, fanny, fundament, hind end, hindquarters, keister, nates, posterior, prat, rear, rear end, rump, seat, stern, tail, tail end, tooshie, tush
anal sphincter, body, body part, imperforate anus, musculus sphincter ani, opening, orifice, porta, rectum, sphincter ani, torso, trunk
\Arse\, n. [AS. ears; [ae]rs; akin to OHG. ars. G. arsch, D. aars, Sw. ars, Dan. arts, Gr. ? (cf. ? tail).] The buttocks, or hind part of an animal; the posteriors; the fundament; the bottom.