act up meaning and examples thumbnail

act up meaning and examples

2025-09-09

Meaning

  • Act up is a phrasal verb with two common meanings:

    1. To behave badly or cause trouble (often used for people, especially children).
    2. To not work properly or malfunction (often used for machines, devices, or even body parts).

Grammar and Usage

  • Verb type: intransitive (does not take a direct object).

  • Structure: subject + act up

    • "The kids are acting up."
    • "My laptop is acting up again."

Common Phrases

  • "The kids are acting up."
  • "My computer is acting up."
  • "His knee is acting up again."

Collocations

  • Children + act up
  • Machine/Device + act up
  • Body part + act up

Examples

  1. The children started acting up during the long car ride.
  2. My phone is acting up—I might need to restart it.
  3. His back is acting up again after lifting those heavy boxes.
  4. The students acted up when the teacher left the room.
  5. The printer acted up and stopped working during the presentation.
  6. Don’t worry, the dog is only acting up because he’s nervous.
  7. The engine acted up on the way home, so we had to stop.
  8. Her old injury started acting up after the marathon.
  • misbehave
  • cause trouble
  • malfunction
  • break down

Antonym

  • behave well
  • function properly
  • run smoothly