secret
noun
ˈsiːkrət 
ˈsiːkrət 
1 [countable] something that is known about by only a few people and not told to othersCan you keep a secret?The location of the ship is a closely guarded secret.Shall we let him in on (= tell him) the secret?He made no secret of his ambition (= he didn't try to hide it).She was dismissed for revealing trade secrets.official/State secretsdark secrets from his past2 (usually the secret) [singular] the best or only way to achieve something; the way a particular person achieves somethingCareful planning is the secret of success.She still looks so young. What's her secret?3 [countable, usually plural] a thing that is not yet fully understood or that is difficult to understandthe secrets of the universeIdioms
in secret
without other people knowing about it
The meeting was held in secret.She admired him, in secret of course.