Source : Webster's Revised Unabridged Dictionary (1913)

Act \Act\, v. t. [imp. & p. p. {Acted}; p. pr. & vb. n.
   {Acting}.] [L. actus, p. p. of agere to drive, lead, do; but
   influenced by E. act, n.]
   1. To move to action; to actuate; to animate. [Obs.]

            Self-love, the spring of motion, acts the soul.
                                                  --Pope.

   2. To perform; to execute; to do. [Archaic]

            That we act our temporal affairs with a desire no
            greater than our necessity.           --Jer. Taylor.

            Industry doth beget by producing good habits, and
            facility of acting things expedient for us to do.
                                                  --Barrow.

            Uplifted hands that at convenient times Could act
            extortion and the worst of crimes.    --Cowper.

   3. To perform, as an actor; to represent dramatically on the
      stage.

   4. To assume the office or character of; to play; to
      personate; as, to act the hero.

   5. To feign or counterfeit; to simulate.

            With acted fear the villain thus pursued. --Dryden.

   {To act a part}, to sustain the part of one of the characters
      in a play; hence, to simulate; to dissemble.

   {To act the part of}, to take the character of; to fulfill
      the duties of.

Acting \Act"ing\, a.
   1. Operating in any way.

   2. Doing duty for another; officiating; as, an acting
      superintendent.

Source : WordNet®

acting
     adj : serving temporarily especially as a substitute; "the acting
           president" [syn: {acting(a)}]
     n : the performance of a part or role in a drama [syn: {playing},
          {playacting}, {performing}]