Secret:
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5.secluded, sheltered, or withdrawn: a secret hiding place.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