Yes, a secret is:
1. done, made, or conducted without the knowledge of others: secret negotiations.
2. kept from the knowledge of any but the initiated or privileged: a secret password.
3. faithful or cautious in keeping confidential matters confidential; close-mouthed; reticent.
4. designed or working to escape notice, knowledge, or observation: a secret drawer; the secret police.
5. secluded, sheltered, or withdrawn: a secret hiding place.
6. beyond ordinary human understanding; esoteric.
7. (of information, a document, etc.) a. bearing the classification secret.
b. limited to persons authorized to use information documents, etc., so classified.