1. secret

something that should remain hidden from others (especially information that is not to be passed on)

Example Sentences:
'the combination to the safe was a secret'
'he tried to keep his drinking a secret'

2. arcanum, secret

information known only to a special group

Example Sentences:
'the secret of Cajun cooking'

• arcanum

3. closed book, enigma, mystery, secret

something that baffles understanding and cannot be explained

Example Sentences:
'how it got out is a mystery'
'it remains one of nature's secrets'

• closed book
• enigma
• mystery

4. secret

not open or public; kept private or not revealed

Example Sentences:
'a secret formula'
'secret ingredients'
'secret talks'

5. clandestine, cloak-and-dagger, hole-and-corner, hugger-mugger, hush-hush, secret, surreptitious, undercover, underground

conducted with or marked by hidden aims or methods

Example Sentences:
'clandestine intelligence operations'
'cloak-and-dagger activities behind enemy lines'
'hole-and-corner intrigue'
'secret missions'
'a secret agent'
'secret sales of arms'
'surreptitious mobilization of troops'
'an undercover investigation'
'underground resistance'

• clandestine
• cloak-and-dagger
• hole-and-corner
• hugger-mugger
• hush-hush
• surreptitious
• undercover
• underground

6. secret, unavowed

not openly made known

Example Sentences:
'a secret marriage'
'a secret bride'

• unavowed

7. secret

communicated covertly

Example Sentences:
'their secret signal was a wink'
'secret messages'

8. private, secret

not expressed

Example Sentences:
'secret (or private) thoughts'

• private

9. hidden, secret

designed to elude detection

Example Sentences:
'a hidden room or place of concealment such as a priest hole'
'a secret passage'
'the secret compartment in the desk'

• hidden

10. privy, secluded, secret

hidden from general view or use

Example Sentences:
'a privy place to rest and think'
'a secluded romantic spot'
'a secret garden'

• privy
• secluded

11. confidential, secret

(of information) given in confidence or in secret

Example Sentences:
'this arrangement must be kept confidential'
'their secret communications'

• confidential

12. secret

indulging only covertly

Example Sentences:
'a secret alcoholic'

13. mysterious, mystic, mystical, occult, orphic, secret

having an import not apparent to the senses nor obvious to the intelligence; beyond ordinary understanding

Example Sentences:
'mysterious symbols'
'the mystical style of Blake'
'occult lore'
'the secret learning of the ancients'

• mysterious
• mystic
• mystical
• occult
• orphic

14. secret

the next to highest level of official classification for documents