adjective

1. kept from public knowledge or from the knowledge of a certain person or persons
2. withdrawn, remote, or secluded a secret hideaway
3. keeping one's affairs to oneself; secretive
4. beyond general knowledge or understanding; mysterious or esoteric
5. concealed from sight or notice; hidden a secret drawer
6. acting in secret a secret society

Etymology: OFr < L secretus, pp. of secernere, to set apart < se-, apart (see secede) + cernere, to sift, distinguish: see harvest

noun

1. something known only to a certain person or persons and purposely kept from the knowledge of others
2. something not revealed, understood, or explained; mystery the secret of Stonehenge
3. the true cause or explanation, regarded as not obvious the secret of one's success
4. a prayer said just before the Preface of the Mass