<p><strong>Adjective</strong></p><ul><li>done, made, or conducted without the knowledge of others: secret negotiations.</li><li>Synonyms: covert, hidden, clandestine.</li><li>Antonyms: manifest, open.</li><li>kept from the knowledge of any but the initiated or privileged: a secret password.</li><li>Synonyms: confidential, private.</li><li>faithful or cautious in keeping confidential matters confidential; close-mouthed; discreet.</li><li>Synonyms: reticent, secretive, close.</li><li>designed or working to escape notice, knowledge, or observation: the secret police.</li><li>secluded, sheltered, or withdrawn: a secret hiding place.</li><li>beyond ordinary human understanding; esoteric.</li><li>Synonyms: mysterious, cryptic, occult.</li><li>(of information, a document, etc.) bearing the classification secret.</li><li>limited to persons authorized to use information documents, etc., so classified.</li></ul><p><strong>Noun</strong></p><ul><li>something that is or is kept secret, hidden, or concealed.</li><li>a mystery: the secrets of nature.</li><li>a reason or explanation not immediately or generally apparent.</li><li>a method, formula, plan, etc., known only to the initiated or the few: a trade secret.</li><li>the secret of happiness; a trade secret.</li><li>a classification assigned to information, a document, etc., considered less vital to security than top-secret but more vital than confidential, and limiting its use to persons who have been cleared, as by various government agencies, as trustworthy to handle such material.</li><li>(initial capital letter) Liturgy: a variable prayer in the Roman and other Latin liturgies, said inaudibly by the celebrant after the offertory and immediately before the preface.</li></ul>