Definition of act verb from the Oxford Advanced American Dictionary

     

    act

     verb
    verb
    NAmE//ækt//
     
    Verb Forms present simple I / you / we / they act
     
    he / she / it acts
     
    past simple acted
     
    -ing form acting
     
     
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    do something
  1. 1 [intransitive] to do something for a particular purpose or in order to deal with a situation It is vital that we act to stop the destruction of the rainforests. The girl's life was saved because the doctors acted so promptly. He claims he acted in self-defense.
  2. behave
  3. 2 [intransitive] to behave in a particular way + adv. John's been acting very strangely lately. act like somebody/something Stop acting like spoiled children! act as if/though… She was acting as if she'd seen a ghost. In spoken English people often use like instead of as if or as though in this meaning:She was acting like she'd seen a ghost.
  4. pretend
  5. 3 [intransitive] to pretend by your behavior to be a particular type of person + adj. I decided to act dumb. He acts all macho, but he's a real softie underneath.
  6. perform in play/movie
  7. 4 [intransitive, transitive] to perform a part in a play or movie Have you ever acted? Most of the cast act well. act something Who's acting (= taking the part of) Hamlet? The play was well acted.
  8. perform function
  9. 5 [intransitive] to perform a particular role or function act as something Can you act as interpreter? A five-year sentence should act as a deterrent to others. act like something hormones in the brain that act like natural painkillers
  10. have effect
  11. 6[intransitive] act (on something) to have an effect on something Alcohol acts quickly on the brain. It took a few minutes for the drug to act.
  12. Idioms Phrasal Verbsˈact for/on behalf of somebodyˈact on/upon somethingˌact somethingˈoutˌact ˈup
See the Oxford Advanced Learner's Dictionary entry: act