stern in WordNet English dictionary

1. the rear part of a ship
   stern  after part  quarter  poop  tail 
   
2. 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 
   

1. of a stern or strict bearing or demeanor; forbidding in aspect
   "an austere expression"; "a stern face"
   austere  stern 
   
2. severely simple
   "a stark interior"
   austere  severe  stark  stern 
   
3. severe and unremitting in making demands
   "an exacting instructor"; "a stern disciplinarian"; "strict standards"
   stern  strict  exacting 
   
4. not to be placated or appeased or moved by entreaty
   "grim determination"; "grim necessity"; "Russia's final hour, it seemed, approached with inexorable certainty"; "relentless persecution"; "the stern demands of parenthood"
   grim  inexorable  relentless  stern  unappeasable  unforgiving  unrelenting