Act Up

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Meaning of Idiom 'Act Up'

1. To act up, usually in regards to children, means to behave badly or cause trouble. 1,2

2. In regards to machinary or electronics, to malfunction or to not operate abnormally. 1,3

3. In regards to medical conditions and their symptoms, to act up means to become active. Often used in regards to allergies. 1


"If you children keep acting up, we are not going to go to the amusement park."

"I don't know what's wrong with my dog, he never acts up like this. Maybe he is sick."

"My computer acted up yesterday so I wasn't able to get my report finished."

"The car is acting up so I'm going to have to take a cab to work today."

"Can you open this jar?" asked Mom. "My arthritis is acting up."

"When my allergies act up I usually just take one pill, but today was a two-pill day!"


Used since around 1900. 3

1. Heacock, Paul. Cambridge Dictionary of American Idioms. Cambridge: Cambridge UP, 2010.
2. Bengelsdorf, Peter. Idioms in the News - 1,000 Phrases, Real Examples. N.p.: Amz Digital Services, 2012.
3. Ammer, Christine. American Heritage Dictionary of Idioms. Boston: Houghton Mifflin Harcourt, 2013.

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