rear end
     n : 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, rump, stern, seat, tail, tail end, tooshie,
          tush, bottom, behind, derriere, fanny, ass
see also:
buttocks nates arse butt backside bum 
buns can fundament hindquarters hind end 
keister posterior prat rear rump 
stern seat tail tail end tooshie 
tush bottom behind derriere fanny 
ass 

33 moby thesaurus words for "rear end":
   afterpart, afterpiece, back, back door, back seat, back side,
   backside, behind, bottom, breech, butt, buttocks, croup, crupper,
   fanny, haunches, heel, hind end, hind part, hindhead, nates,
   occiput, posterior, postern, rear, rearward, reverse, rump, seat,
   stern, tail, tail end, tailpiece