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adjective American English pronunciation: mysterious /mɪˈstɪriəs/
  1. 1
    not explained or understood

    They are investigating the mysterious disappearance of a young man.

    mysterious circumstances:

    He died in mysterious circumstances.

    1. a.
      not recognized or known

      a mysterious woman in a white suit

      a mysterious illness

  2. 2
    keeping things secret, especially in a way that makes other people want to discover what they are

    Stop being so mysterious and tell us what happened!

    1. a.
      full of secrets

      The rugged mountains in the distance were dark and mysterious.

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