Definition of secret :
1. A thing not discovered; what is unknown or unexplained; a mystery.
2. Faithful to a secret; not inclined to divulge or betray confidence; secretive.
3. Hidden; concealed; as, secret treasure; secret plans; a secret vow.
4. Separate; distinct.
5. Something studiously concealed; a thing kept from general knowledge; what is not revealed, or not to be revealed.
6. The parts which modesty and propriety require to be concealed; the genital organs.
7. To keep secret.
8. Withdraw from general intercourse or notice; in retirement or secrecy; secluded.
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concealed (part of speech: adjective)
secret (part of speech: adjective)
private (part of speech: adjective)