rump in WordNet English dictionary

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?"
   buttocks  nates  arse  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. the part of an animal that corresponds to the human buttocks
   hindquarters  croup  croupe  rump 
   
3. fleshy hindquarters; behind the loin and above the round
   rump