n. & v.
1. the fact or process of doing or acting (demanded action; put ideas into action).
2 forcefulness or energy as a characteristic (a woman of action).
3 the exertion of energy or influence (the action of acid on metal).
4 something done; a deed or act (not aware of his own actions).
5 a a series of events represented in a story, play, etc. b sl. exciting activity (arrived late and missed the action; want some action).
6 a armed conflict; fighting (killed in action). b an occurrence of this, esp. a minor military engagement.
7 a the way in which a machine, instrument, etc. works (explain the action of an air pump). b the mechanism that makes a machine, instrument, etc. (e.g. a musical instrument, a gun, etc.) work. c the mode or style of movement of an animal or human (usu. described in some way) (a runner with good action).
8 a legal process; a lawsuit (bring an action).
9 (in imper.) a word of command to begin, esp. used by a film director etc.
--v.tr. bring a legal action against.
Phrases and idioms:
action committee (or group etc.) a body formed to take active steps, esp. in politics. action-packed colloq. full of action or excitement. action painting an aspect of abstract expressionism with paint applied by the artist's random or spontaneous gestures. action point a proposal for action, esp. arising from a discussion etc. action replay a playback of part of a television broadcast, esp. a sporting event, often in slow motion. action stations positions taken up by troops etc. ready for battle. go into action start work. out of action not working. take action begin to act (esp. energetically in protest).
Etymology: ME f. OF f. L actio -onis (as ACT)