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 typewriter 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
Matthew Futterman, The Athletic, 7 Mar. 2025
The hourlong descent appeared to go well until the final approach when the laser navigation system began acting up.
—Marcia Dunn, Los Angeles Times, 6 Mar. 2025
An audio issue or two aside, Netflix mostly didn’t act up.
—Jennifer Zhan, Vulture, 24 Feb. 2025
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, 18 Jan. 2025
See All Example Sentences for act up
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Verb
Her pain can act up suddenly and seemingly comes without rhyme or reason.
—Matthew Futterman, The Athletic, 7 Mar. 2025
The hourlong descent appeared to go well until the final approach when the laser navigation system began acting up.
—Marcia Dunn, Los Angeles Times, 6 Mar. 2025
An audio issue or two aside, Netflix mostly didn’t act up.
—Jennifer Zhan, Vulture, 24 Feb. 2025
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, 18 Jan. 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 12 Mar. 2025.
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