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]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "autonomous":
   absolute, arbitrary, aristocratic, autarchic, autarkic,
   authoritarian, autocratic, bureaucratic, civic, civil,
   constitutional, democratic, despotic, dictatorial, discretional,
   discretionary, elective, fascist, federal, federalist,
   federalistic, free, free will, free-spirited, freewheeling,
   governmental, gratuitous, gubernatorial, heteronomous, independent,
   individualistic, inner-directed, matriarchal, matriarchic,
   monarchal, monarchial, monarchic, monocratic, neutral, nonaligned,
   nonmandatory, nonpartisan, offered, official, oligarchal,
   oligarchic, optional, parliamentarian, parliamentary, patriarchal,
   patriarchic, pluralistic, political, proffered, republican,
   self-acting, self-active, self-contained, self-dependent,
   self-determined, self-determining, self-directing, self-governed,
   self-governing, self-reliant, self-subsistent, self-sufficient,
   self-supporting, separate, sovereign, spontaneous, theocratic,
   third-force, third-world, totalitarian, unasked, unbesought,
   unbidden, uncalled-for, uncoerced, uncompelled, unconstrained,
   uncontrolled, unforced, uninfluenced, uninvited, unpressured,
   unprompted, unrequested, unrequired, unsolicited, unsought,
   voluntary, volunteer, willful