mystery mystery /ˈmɪstɝi/

noun

1. () Something that baffles understanding and cannot be explained  ( closed book , secret , enigma , mystery )
   something that baffles understanding and cannot be explained
    How it got out is a mystery
   how it got out is a mystery
    It remains one of nature's secrets
   it remains one of nature's secrets
   
2. A story about a crime (usually murder) presented as a novel, play or movie  ( mystery , whodunnit [British] , whodunit [Informal] , mystery story )
   a story about a crime (usually murder) presented as a novel, play or movie
     She curled up with a thrilling mystery story before bedtime.
   She curled up with a thrilling mystery story before bedtime.