ac·tion
[ak-shuh n]

noun
1. the process or state of acting or of being active: The machine is not in action now.

2. something done or performed; act; deed.

3. an act that one consciously wills and that may be characterized by physical or mental activity: a crisis that demands action instead of debate; hoping for constructive action by the landlord.

4. actions, habitual or usual acts; conduct: He is responsible for his actions.

5. energetic activity: a man of action.

6. an exertion of power or force: the action of wind upon a ship’s sails.

7. effect or influence: the action of morphine.

8. Physiology . a change in organs, tissues, or cells leading to performance of a function, as in muscular contraction.

9. way or manner of moving: the action of a machine or of a horse.

10. the mechanism by which something is operated, as that of a gun or a piano.

11. a military encounter or engagement; battle, skirmish, or the like.

12. actual engagement in fighting an enemy; military or naval combat: He saw action in Vietnam.

13. Literature . the main subject or story, as distinguished from an incidental episode.

14. Theater .    
     a. an event or series of events that form part of a dramatic plot: the action of a scene.
     b.one of the three unities. Compare unity ( def. 8 ) .

15. the gestures or deportment of an actor or speaker.

16. Fine Arts . the appearance of animation, movement, or emotion given to figures by their attitude, position, or expression.

17. Law .
     a. a proceeding instituted by one party against another.
     b. the right of bringing it.

18. Slang .
     a. interesting or exciting activity,  often of an illicit nature: He gave us some tips on where the action was.
     b. gambling or the excitement of gambling: The casino usually offers plenty of action.
     c. money bet in gambling, especially illegally.

19. Ecclesiastical .
     a. a religious ceremony, especially a Eucharistic service.
     b. the canon of the Mass.
     c. those parts of a service of worship in which the congregation participates.

adjective
20. characterized by brisk or dynamic action: an action car; an action melodrama.

Idioms
21. in action,
     a. performing or taking part in a characteristic act: The school baseball team is in action tonight.
     b. working; functioning: His rescuing the child was bravery in action.

22. out of action, removed from action, as by sudden disability: The star halfback is out of action with a bad knee.

23. piece of the action, Informal . a share of the proceeds or profits: Cut me in for a piece of the action.

24. take action,
     a.to start doing something: As soon as we get his decision, we’ll take action.
     b. to start a legal procedure.