Definition of "Secret" :

noun: something that baffles understanding and cannot be explained

"It remains one of nature's secrets."

noun: information known only to a special group

"The secret of Cajun cooking."

noun: something that should remain hidden from others (especially information that is not to be passed on)

"The combination to the safe was a secret."

adjective: not openly made known

"A secret marriage."

adjective: the next to highest level of official classification for documents

adjective: having an import not apparent to the senses nor obvious to the intelligence; beyond ordinary understanding

"The secret learning of the ancients."

adjective: not expressed

"Secret (or private) thoughts."

adjective: conducted with or marked by hidden aims or methods

"Secret missions."

adjective: indulging only covertly

"A secret alcoholic."

adjective: communicated covertly

"Their secret signal was a wink."

adjective: (of information) given in confidence or in secret

"Their secret communications."

adjective: hidden from general view or use

"A secret garden."

adjective: designed to elude detection

"A secret passage."

adjective: not open or public; kept private or not revealed

"A secret formula."