monster in WordNet English dictionary

1. someone or something that is abnormally large and powerful
   giant  goliath  behemoth  monster  colossus 
   
2. a cruel wicked and inhuman person
   monster  fiend  devil  demon  ogre 
   
3. a person or animal that is markedly unusual or deformed
   freak  monster  monstrosity  lusus naturae 
   
4. (medicine) a grossly malformed and usually nonviable fetus
   monster  teras 
   
5. an imaginary creature usually having various human and animal parts
   monster