tough in WordNet English dictionary

1. feeling physical discomfort or pain (`tough' is occasionally used colloquially for `bad')
   "my throat feels bad"; "she felt bad all over"; "he was feeling tough after a restless night"
   bad  tough 
   
2. making great mental demands; hard to comprehend or solve or believe
   "a baffling problem"; "I faced the knotty problem of what to have for breakfast"; "a problematic situation at home"
   baffling  elusive  knotty  problematic  problematical  tough 
   
3. unfortunate or hard to bear
   "had hard luck"; "a tough break"
   hard  tough 
   
4. violent and lawless
   "the more ruffianly element"; "tough street gangs"
   ruffianly  tough 
   
5. very difficult; severely testing stamina or resolution
   "a rugged competitive examination"; "the rugged conditions of frontier life"; "the competition was tough"; "it's a tough life"; "it was a tough job"
   rugged  tough 
   
6. substantially made or constructed
   "sturdy steel shelves"; "sturdy canvas"; "a tough all-weather fabric"; "some plastics are as tough as metal"
   sturdy  tough 
   
7. resistant to cutting or chewing
   tough 
   
8. physically toughened
   "the tough bottoms of his feet"
   tough  toughened 
   
9. not given to gentleness or sentimentality
   "a tough character"
   tough 
   

1. a cruel and brutal fellow
   bully  tough  hooligan  ruffian  roughneck  rowdy  yob  yobo  yobbo 
   
2. an aggressive and violent young criminal
   hood  hoodlum  goon  punk  thug  tough  toughie  strong-armer 
   
3. someone who learned to fight in the streets rather than being formally trained in the sport of boxing
   street fighter  tough