Source : Webster's Revised Unabridged Dictionary (1913)

Arse \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.

Source : WordNet®

arse
     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},
           {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: excretory opening at the end of the alimentary canal [syn: {anus},
         {arsehole}, {asshole}]