secret
adjective
uk/ˈsiːkrət/ usif something is secret, only particular people are allowed to know about it:
secret deal/meeting/talks
Staff were informed to keep the company's plans secret.
a secret document/operation/proposal
See also
top-secret
secret
noun [ C ]
uk/ˈsiːkrət/ usan important piece of information that only a few people know and that should not be told to anyone else:
The ingredients of the drink are a closely-guarded secret.
a national/military/state secret
See also
trade secret