American English

Definition of act noun from the Oxford Advanced American Dictionary



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    something that someone does
  1. 1[countable] a particular thing that someone does a criminal act act of something an act of kindness acts of terrorism act of somebody The murder was the act of a psychopath. Thesaurusactionmeasure step act moveThese are all words for a thing that someone does.action a thing that someone does:Her quick action saved the child's life.measure an official action that is done in order to achieve a particular aim:The government introduced tougher security measures last summer.step one of a series of things that you do in order to achieve something:This work is a first step towards our eventual goal.act a thing that someone does:an act of kindnessaction or act?These two words have the same meaning but are used in different patterns. An act is usually followed by of and/or used with an adjective. Action is not usually used with of but is often used with his, her, etc.:a heroic act of bravery a heroic action of bravery her heroic actions/acts during the war.Action often combines with take but act does not:We will take whatever action is necessary. We will take whatever acts are necessary.move (used especially in journalism) an action that you do or need to do to achieve something:They are waiting for the results of the opinion polls before deciding their next move.Patterns to take action/measures/steps to make a move a heroic/brave/daring action/step/act/move
  2. law
  3. 2[countable] a law that has been passed by a government an act of Congress the Civil Rights Act A committee on Safety of Medicines was set up under the Act.
  4. pretending
  5. 3[singular] a way of behaving that is not sincere but is intended to have a particular effect on others Don't take her seriously—it's all an act. You could tell she was just putting on an act.
  6. in play/entertainment
  7. 4[countable] one of the main divisions of a play, an opera, etc. a play in five acts The hero dies in Act 5, Scene 3.
  8. 5[countable] one of several short pieces of entertainment in a show a circus/comedy/magic act
  9. 6[countable] a performer or group of musicians They were one of rock's most impressive live acts.
  10. Idioms
    act of God (law)
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    an event caused by natural forces beyond human control, such as a storm, a flood, or an earthquake
    be/get in on the act (informal)
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    to be/become involved in an activity that someone else has started, especially to get something for yourself New companies want to get in on the act and provide cable services.
    clean up your act (informal)
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    to start behaving in a moral or responsible way He cleaned up his act and got a job.
    do, perform, stage, etc. a disappearing/vanishing act (informal)
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    to go away or be impossible to find when people need or want you
    get your act together (informal)
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    to organize yourself and your activities in a more effective way in order to achieve something He needs to get his act together if he's going to pass.
    a hard/tough act to follow
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    a person who is so good or successful at something that it will be difficult for anyone else coming after them to be as good or successful She has been an excellent principal and will be a hard act to follow.
    in the act (of doing something)
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    while you are doing something He was caught in the act of stealing a car. It is often difficult to tell when someone is using drugs unless they are caught in the act.
    read (somebody) the riot act
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    to tell someone with force that they must not do something
See the Oxford Advanced Learner's Dictionary entry: act