The Collaborative International Dictionary of English v.0.48:

Mystic \Mys"tic\, Mystical \Mys"tic*al\, a. [L. mysticus, Gr. ?
   belonging to secret rites, from ? one initiated: cf. F.
   mystique. See 1st Mystery, Misty.]
   1. Remote from or beyond human comprehension; baffling human
      understanding; unknowable; obscure; mysterious.
      [1913 Webster]

            Heaven's numerous hierarchy span
            The mystic gulf from God to man.      --Emerson.
      [1913 Webster]

            God hath revealed a way mystical and supernatural.
                                                  --Hooker.
      [1913 Webster]

   2. Importing or implying mysticism; involving some secret
      meaning; allegorical; emblematical; as, a mystic dance;
      mystic Babylon.
      [1913 Webster]

            Thus, then, did the spirit of unity and meekness
            inspire every joint and sinew of the mystical body.
                                                  --Milton.
      [1913 Webster]

   3. employing mysticism; as, mystical intuition; mystical
      explanations; -- contrasted to logical, rational,
      analytical.
      [WordNet 1.5] -- Mys"tic*al*ly, adv. --
      Mys"tic*al*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mystically
    adv 1: in a mystical manner; "chant mystically"