hidden in WordNet English dictionary

1. not accessible to view
   "concealed (or hidden) damage"; "in stormy weather the stars are out of sight"
   concealed  hidden  out of sight 
   
2. difficult to find
   "hidden valleys"; "a hidden cave"; "an obscure retreat"
   hidden  obscure 
   
3. designed to elude detection
   "a hidden room or place of concealment such as a priest hole"; "a secret passage"; "the secret compartment in the desk"
   hidden  secret