1. [n]  something that people do or cause to happen
2. [n]  a legal document codifying the result of deliberations of a committee or society or legislative body
3. [n]  a short theatrical performance that is part of a longer program; "he did his act three times every evening"; "she had a catchy little routine"; "it was one of the best numbers he ever did"
4. [n]  a subdivision of a play or opera or ballet
5. [n]  a manifestation of insincerity; "he put on quite an act for her benefit"
6. [v]  behave in a certain manner; show a certain behavior; conduct or comport oneself; "You should act like an adult"; "Don't behave like a fool"; "What makes her do this way?"; "The dog acts ferocious, but he is really afraid of people"
7. [v]  pretend to have certain qualities or state of mind; "He acted the idiot"; "She plays deaf when the news are bad"
8. [v]  discharge one's duties; "She acts as the chair"; "In what capacity are you acting?"
9. [v]  play a role or part; "Gielgud played Hamlet"; "She wants to act Lady Macbeth, but she is too young for the role"; "She played the servant to her husband's master"
10. [v]  perform on a stage or theater; "She acts in this play"; "He acted in"Julius Caesar"; "I played in"A Christmas Carol"
11. [v]  behave unnaturally or affectedly; "She's just acting"
12. [v]  perform an action, or work out or perform (an action); "think before you act"; "We must move quickly"; "The governor should act on the new energy bill"; "The nanny acted quickly by grabbing the toddler and covering him with a wet towel"
13. [v]  be engaged in an activity, often for no particular purpose other than pleasure
14. [v]  have an effect or outcome; often the one desired or expected; "The voting process doesn't work as well as people thought"; "How does your idea work in practice?"; "This method doesn't work"; "The breaks of my new car act quickly"; "The medicine works only if you take it with a lot of water"
15. [v]  be suitable for theatrical performance; "This scene acts well"

ACT is a 3 letter word that starts with A.

1. \Act\ ([a^]kt), n. [L. actus, fr. agere to drive, do: cf. F.
   acte. See {Agent}.]
   1. That which is done or doing; the exercise of power, or the
      effect, of which power exerted is the cause; a
      performance; a deed.
            That best portion of a good man's life, His little,
            nameless, unremembered acts Of kindness and of love.
                                                  --Wordsworth.
      Hence, in specific uses:
      (a) The result of public deliberation; the decision or
          determination of a legislative body, council, court of
          justice, etc.; a decree, edit, law, judgment, resolve,
          award; as, an act of Parliament, or of Congress.
      (b) A formal solemn writing, expressing that something has
          been done. --Abbott.
      (c) A performance of part of a play; one of the principal
          divisions of a play or dramatic work in which a
          certain definite part of the action is completed.
      (d) A thesis maintained in public, in some English
          universities, by a candidate for a degree, or to show
          the proficiency of a student.
   2. A state of reality or real existence as opposed to a
      possibility or possible existence. [Obs.]
            The seeds of plants are not at first in act, but in
            possibility, what they afterward grow to be.
                                                  --Hooker.
   3. Process of doing; action. In act, in the very doing; on
      the point of (doing). ``In act to shoot.'' --Dryden.
            This woman was taken . . . in the very act. --John
                                                  viii. 4.
   {Act of attainder}. (Law) See {Attainder}.
   {Act of bankruptcy} (Law), an act of a debtor which renders
      him liable to be adjudged a bankrupt.
   {Act of faith}. (Ch. Hist.) See {Auto-da-F['e]}.
   {Act of God} (Law), an inevitable accident; such
      extraordinary interruption of the usual course of events
      as is not to be looked for in advance, and against which
      ordinary prudence could not guard.
   {Act of grace}, an expression often used to designate an act
      declaring pardon or amnesty to numerous offenders, as at
      the beginning of a new reign.
   {Act of indemnity}, a statute passed for the protection of
      those who have committed some illegal act subjecting them
      to penalties. --Abbott.
   {Act in pais}, a thing done out of court (anciently, in the
      country), and not a matter of record.
   Syn: See {Action}.
   

2. \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.
   

3. \Act\, v. i.
   1. To exert power; to produce an effect; as, the stomach acts
      upon food.
   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.
            He hangs between, in doubt to act or rest. --Pope.
   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.
   4. To perform on the stage; to represent a character.
            To show the world how Garrick did not act. --Cowper.
   {To act as} or {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.
   

1. annual change traffic.

2. ada core technologies.