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to act up

to act up

28 4.8
To behave badly or to stop working properly
  • phrasal verb
  • /ækt ʌp/
  • Informal
translation icon : comportarse mal
  • Why you gotta act up every time we go someplace?

Maybe once they start acting up, you call the event done.

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Examples

  • The computer's acting up again.

  • And I think that as a parent, now that I'm in that position and my child acts up, yeah, of course we have to discipline them.

  • Maybe once they start acting up, you call the event done.

  • Like people are acting up a bit, you know what I mean?

  • The little guy's been acting up.

  • Is that thing acting up again?

  • When children don't get the love they need, they act up enough to get on their parents' nerves.

    Fiction book (1994)
  • And my husband's gout is acting up, so he couldn't do much walking.

    Blog text (7)
  • Students do not have to worry about favoritism from instructors or class clowns acting up in class.

    Academic text (2010)
  • When the children act up during class, it makes it hard for the teacher to maintain order.

Synonyms

to carry on
vsto act up
  • Informal
53 4.2

To behave in a silly or noisy way that annoys people

covers more serious disruption and also equipment that fails to work
to misbehave
vsto act up
37 2.8

To act in a rude way or break rules

also covers things failing to work, not only bad behavior
to act out
vsto act up
32 5.5

Show strong feelings by behaving badly instead of talking

can also mean failing to work properly, not only emotional expression

Antonyms

3 3.1

Working as it should and ready to use

1 1.2

A child or pet that acts politely and calmly

How Disruptive

to throw a tantrum
  • Informal
18 4.4
to act up
  • Informal
28 4.8
to misbehave
37 2.8

Surface Forms

act up infinitive
acted up past
acted up past participle
acting up present participle
acts up third person singular

Morphology

act + up

The base verb 'act' (to behave) makes the human-behaviour sense partly derivable, but the particle 'up' does not literally mean 'badly' or 'malfunction' and its contribution is idiomatic and variable. Because the combination suggests abnormal or problematic behaviour/malfunction but requires familiarity with phrasal-verb patterns to predict both human and mechanical senses, the expression is only partially predictable to a B1 learner.

Etymology

Act up can also mean to misbehave or stop working properly. Think of act (behave) plus up (more extreme) — a child, a dog, or a machine that suddenly 'acts' in a noisy or wrong way and causes trouble. So act up means 'to behave badly' or 'not work properly'.