The Collaborative International Dictionary of English v.0.48:

Automaton \Au*tom"a*ton\, n.; pl. L. Automata, E.
   Automatons. [L. fr. Gr. ?, neut. of ? self-moving; ? self +
   a root ma, man, to strive, think, cf. ? to strive. See
   Mean, v. i.]
   1. Any thing or being regarded as having the power of
      spontaneous motion or action. --Huxley.
      [1913 Webster]

            So great and admirable an automaton as the world.
                                                  --Boyle.
      [1913 Webster]

            These living automata, human bodies.  --Boyle.
      [1913 Webster]

   2. A self-moving machine, or one which has its motive power
      within itself; -- applied chiefly to machines which appear
      to imitate spontaneously the motions of living beings,
      such as men, birds, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

automaton
    n 1: someone who acts or responds in a mechanical or apathetic
         way; "only an automaton wouldn't have noticed" [syn:
         automaton, zombi, zombie]
    2: a mechanism that can move automatically [syn: automaton,
       robot, golem]

The Free On-line Dictionary of Computing (30 December 2018):

automaton
automata
automata theory

    (Plural automata) A
   machine, robot, or formal system designed to follow a
   precise sequence of instructions.

   Automata theory, the invention and study of automata, includes
   the study of the capabilities and limitations of computing
   processes, the manner in which systems receive input, process
   it, and produce output, and the relationships between
   behavioural theories and the operation and use of automated
   devices.

   See also cellular automaton, finite state machine.

   (1996-04-23)