confidential in WordNet English dictionary

1. the level of official classification for documents next above restricted and below secret; available only to persons authorized to see documents so classified
   confidential 
   
2. denoting confidence or intimacy
   "a confidential approach"; "in confidential tone of voice"
   confidential 
   
3. entrusted with private information and the confidence of another
   "a confidential secretary"
   confidential 
   
4. (of information) given in confidence or in secret
   "this arrangement must be kept confidential"; "their secret communications"
   confidential  secret