noun (n)

• something that baffles understanding and cannot be explained(noun.cognition)

  Example:
  How it got out is a mystery.
  

  Synonym:
  closed book, enigma, secret
  

  source: wordnet30
• a story about a crime (usually murder) presented as a novel or play or movie(noun.communication)

  Synonym:
  mystery story, whodunit
  

  source: wordnet30
• A profound secret; something wholly unknown, or something kept cautiously concealed, and therefore exciting curiosity or wonder; something which has not been or can not be explained; hence, specifically, that which is beyond human comprehension.(noun)

  source: webster1913
• A trade; a handicraft; hence, any business with which one is usually occupied.(noun)

  source: webster1913