The Collaborative International Dictionary of English v.0.48:

Autonomous \Au*ton"o*mous\, a. [Gr. ?; ? self + ? to assign,
   hold, sway.]
   1. Independent in government; having the right or power of
      self-government.
      [1913 Webster]

   2. (Biol.) Having independent existence or laws.
      [1913 Webster]

WordNet (r) 3.0 (2006):

autonomous
    adj 1: (of political bodies) not controlled by outside forces;
           "an autonomous judiciary"; "a sovereign state" [syn:
           autonomous, independent, self-governing,
           sovereign]
    2: existing as an independent entity; "the partitioning of India
       created two separate and autonomous jute economies"
    3: (of persons) free from external control and constraint in
       e.g. action and judgment [syn: autonomous, self-directed,
       self-reliant]