The Collaborative International Dictionary of English v.0.48:

Act \Act\, v. i.
   1. To exert power; to produce an effect; as, the stomach acts
      upon food.
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   2. To perform actions; to fulfill functions; to put forth
      energy; to move, as opposed to remaining at rest; to carry
      into effect a determination of the will.
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            He hangs between, in doubt to act or rest. --Pope.
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   3. To behave or conduct, as in morals, private duties, or
      public offices; to bear or deport one's self; as, we know
      not why he has acted so.
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   4. To perform on the stage; to represent a character.
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            To show the world how Garrick did not act. --Cowper.
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   To act as or To act for, to do the work of; to serve as.


   To act on, to regulate one's conduct according to.

   To act up to, to equal in action; to fulfill in practice;
      as, he has acted up to his engagement or his advantages.
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