Synonyms of confidential

1 Syllable
hushed
2 Syllables
privy, backstairs, backdoor, chummy, chummier, clubbier, clubby, hush-hush, screened, closet, withheld
3 Syllables
unlisted, classified, arcane, blockaded, inside, private, secluded, nonpublic
4 Syllables
buddy-buddy, intimate, unreported, huggermugger, undercover, undisclosed
5 Syllables
under-the-table, unregistered, unpublicized