The Collaborative International Dictionary of English v.0.48:

Autocracy \Au*toc"ra*cy\, n.; pl. Autocracies. [Gr. ?: cf. F.
   autocratie. See Autocrat.]
   1. Independent or self-derived power; absolute or controlling
      authority; supremacy.
      [1913 Webster]

            The divine will moves, not by the external impulse
            or inclination of objects, but determines itself by
            an absolute autocracy.                --South.
      [1913 Webster]

   2. Supreme, uncontrolled, unlimited authority, or right of
      governing in a single person, as of an autocrat.
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   3. Political independence or absolute sovereignty (of a
      state); autonomy. --Barlow.
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   4. (Med.) The action of the vital principle, or of the
      instinctive powers, toward the preservation of the
      individual; also, the vital principle. [In this sense,
      written also autocrasy.] --Dunglison.
      [1913 Webster]

WordNet (r) 3.0 (2006):

autocracy
    n 1: a political system governed by a single individual [syn:
         autocracy, autarchy]
    2: a political theory favoring unlimited authority by a single
       individual