acted up; acting up; acts up
1
: to act in a way different from that which is normal or expected: such as
a
: to behave in an unruly, recalcitrant, or capricious manner
The children were acting up.
b
: show off
c
: to function improperly
This keyboard is acting up again.
2
: to become active or acute after being quiescent
Her rheumatism started to act up.
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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
Daley Quinn, Southern Living, 13 Nov. 2025
Its general sensibility seems more Superstore than The Office, down to the interstitial montages of customers acting up in the perpetually overcrowded waiting room.
—Angie Han, HollywoodReporter, 13 Oct. 2025
Sturm said his back started acting up after the team’s first practice.
—Michael Russo, New York Times, 1 Oct. 2025
In the cold and austere German winter (a far cry from Dakar’s physical and cultural warmth), an anxious Nourou acts up outside a hotel and is accosted by a Polish security guard, setting off a minor chain reaction in which Maja intervenes on his behalf, much to his chagrin.
—Siddhant Adlakha, Variety, 28 Sep. 2025
See All Example Sentences for act up
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Verb
Allergies acting up: Homeowners who are sensitive to dust, pollen, or animal hair may notice their allergies acting up before anything else.
—Daley Quinn, Southern Living, 13 Nov. 2025
Its general sensibility seems more Superstore than The Office, down to the interstitial montages of customers acting up in the perpetually overcrowded waiting room.
—Angie Han, HollywoodReporter, 13 Oct. 2025
Sturm said his back started acting up after the team’s first practice.
—Michael Russo, New York Times, 1 Oct. 2025
In the cold and austere German winter (a far cry from Dakar’s physical and cultural warmth), an anxious Nourou acts up outside a hotel and is accosted by a Polish security guard, setting off a minor chain reaction in which Maja intervenes on his behalf, much to his chagrin.
—Siddhant Adlakha, Variety, 28 Sep. 2025
See All Example Sentences for act up
Cite this Entry
“Act up.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/act%20up. Accessed 29 Nov. 2025.
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