act up
Britishverb
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Misbehave. For example, With an inexperienced rider, this horse always acts up . [c. 1900]
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Malfunction, as in I'm not sure what's wrong with my car, but the transmission is acting up . In both usages up means “abnormally.”
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
“That’s not the idea. The idea is to have them clean their act up so that they do better and the stock goes up and their dividends go up,” Ryan said.
From Seattle Times • Feb. 26, 2024
The more serious the occasion, the more he'll act up.
From BBC • Oct. 24, 2022
My granddaughters get upset, act up and give her a hard time, and I can understand why.
From Washington Post • Aug. 31, 2022
Lopez says she hopes to keep playing for many years, even if her knee is starting to act up a bit.
From Reuters • Aug. 5, 2022
Wes didn’t act up in class, which kept him under the radar; his teachers spent 90 percent of their time dealing with the 5 percent of kids who did.
From "The Other Wes Moore: One Name, Two Fates" by Wes Moore
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
