secret
Not openly made known.
“a secret marriage”
“a secret bride”
Communicated covertly.
“their secret signal was a wink”
“secret messages”
Indulging only covertly.
“a secret alcoholic”
Not open or public; kept private or not revealed.
“a secret formula”
“secret ingredients”
The next to highest level of official classification for documents.
Conducted with or marked by hidden aims or methods.
“secret missions”
“a secret agent”
Hidden from general view or use.
“a secret garden”
Not expressed.
“secret (or private) thoughts”
(of information) given in confidence or in secret.
“their secret communications”
Having an import not apparent to the senses nor obvious to the intelligence; beyond ordinary understanding.
“the secret learning of the ancients”
Designed to elude detection.
“a secret passage”
“the secret compartment in the desk”
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”
Something that baffles understanding and cannot be explained.
“it remains one of nature's secrets”
Information known only to a special group.
“the secret of Cajun cooking”