act up

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acted up; acting up; acts up

intransitive verb

: to act in a way different from that which is normal or expected: such as
: to behave in an unruly, recalcitrant, or capricious manner
the children were acting up
: to function improperly
this typewriter is acting up again
: to become active or acute after being quiescent
her rheumatism started to act up


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AIDS Coalition to Unleash Power

Examples of act up in a Sentence

Verb the two-year-old was acting up in church so much that her dad had to take her outside you should have seen the boys acting up when they put on their aprons
Recent Examples on the Web
Babies remain the last vestige of scoundrels in sequel terms, so naturally the movie introduces a son to Gru (voiced as usual by Steve Carell) and Lucy (Kristen Wiig) who, semi-amusingly, can’t stand his dad, screaming or acting up in some other way every time Gru picks him up. Brian Lowry, CNN, 2 July 2024 Nobody's that good an actor to keep this act up for 50 years. Daniela Avila, Peoplemag, 27 June 2024 The parents of children who act up in the Jersey Shore town of Margate City will be fined this summer for their badly behaved kids. Brian Niemietz, New York Daily News, 13 June 2024 In November of last year, the car started acting up — the transmission seemed to have failed after just a few months of ownership. Andy Kalmowitz / Jalopnik, Quartz, 11 June 2024 But after two years, Cunningham cut off any contact, saying AJ acted up after being with her. Robert McCoppin, Chicago Tribune, 6 June 2024 But his elbow acted up in a live bullpen session before the American League Division Series, forcing the Orioles to put him on the shelf and keep him off their playoff roster. Jacob Calvin Meyer, Baltimore Sun, 21 Mar. 2024 Eury Perez, the Marlins’ 20-year-old phenom, underwent Tommy John surgery himself on Monday after his elbow began acting up midway through spring training. Jordan McPherson, Miami Herald, 10 Apr. 2024 The biggest trophy of the night is for video of the year, which originally saw 16 acts up for the coveted belt buckle. Sadie Bell, Peoplemag, 6 Apr. 2024

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'act up.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use


1879, in the meaning defined at sense 1

Time Traveler
The first known use of act up was in 1879

Dictionary Entries Near act up

Cite this Entry

“Act up.” Dictionary, Merriam-Webster, Accessed 20 Jul. 2024.

Kids Definition

act up

: to act in an unruly, abnormal, or annoying way
Last Updated: - Updated example sentences
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