confidential

/ˈkɑnfəˌdɛntʃəl/

/kɒnfɪˈdɛnʃəl/

If you get a letter stamped confidential, that means you're not supposed to tell anyone else what it says. It's private and you're not supposed to blab about it.

Confidential suggests that you're being let in on a secret — as in Kitchen Confidential, the title of a book by Anthony Bourdain, a famous chef, in which he tells unappetizing stories about the restaurant industry. If you confide in someone, you are trusting him or her with confidential or secret information. Choose your confidants wisely!

Definitions of confidential

1. adjective

   (of information) given in confidence or in secret
   “this arrangement must be kept confidential”

   synonyms: secret

   private

   confined to particular persons or groups or providing privacy
2. adjective

   entrusted with private information and the confidence of another
   “a confidential secretary”

   synonyms:

   private

   confined to particular persons or groups or providing privacy
3. adjective

   denoting confidence or intimacy
   “a confidential approach”

   “in confidential tone of voice”

   synonyms:

   close

   close in relevance or relationship
4. adjective

   the level of official classification for documents next above restricted and below secret; available only to persons authorized to see documents so classified
   synonyms:

   classified

   official classification of information or documents; withheld from general circulation