WordWeb Online

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

See also: classified, close, private

Encyclopedia: Confidential