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Verb: act up
  1. Misbehave badly; act in a silly or improper way
    "The children acted up when they were not bored";
    - carry on
     
  2. Make itself felt as a recurring pain
    "My arthritis is acting up again"
     
  3. [informal] Function erratically; stop working reliably
    - play up [Brit, informal]

Derived forms: acts up, acting up, acted up

See also: behave

Type of: ache, hurt, misbehave, misconduct, misdemean, smart

Encyclopedia: Act up