The noun secret has 3 senses (first 1 from tagged texts)
1. (9) secret -- (something that should remain hidden from others (especially information that is not to be passed on); "the combination to the safe was a secret"; "he tried to keep his drinking a secret")
2. secret, arcanum -- (information known only to a special group; "the secret of Cajun cooking")
3. mystery, enigma, secret, closed book -- (something that baffles understanding and cannot be explained; "how it got out is a mystery"; "it remains one of nature's secrets")
Overview of adj secret
The adj secret has 11 senses (first 5 from tagged texts)
1. (11) secret -- (not open or public; kept private or not revealed; "a secret formula"; "secret ingredients"; "secret talks")
2. (2) clandestine, cloak-and-dagger, hole-and-corner, hugger-mugger, hush-hush, secret, surreptitious, undercover, underground -- (conducted with or marked by hidden aims or methods; "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")
3. (2) unavowed, secret -- (not openly made known; "a secret marriage"; "a secret bride")
4. (1) secret -- (communicated covertly; "their secret signal was a wink"; "secret messages")
6. hidden, secret -- (designed to elude detection; "a hidden room or place of concealment such as a priest hole"; "a secret passage"; "the secret compartment in the desk")
7. privy, secluded, secret -- (hidden from general view or use; "a privy place to rest and think"; "a secluded romantic spot"; "a secret garden")
8. confidential, secret -- ((of information) given in confidence or in secret; "this arrangement must be kept confidential"; "their secret communications")
9. secret -- (indulging only covertly; "a secret alcoholic")
10. mysterious, mystic, mystical, occult, secret, orphic -- (having an import not apparent to the senses nor obvious to the intelligence; beyond ordinary understanding; "mysterious symbols"; "the mystical style of Blake"; "occult lore"; "the secret learning of the ancients")
11. secret -- (the next to highest level of official classification for documents)