act up
Britishverb
-
Misbehave. For example, With an inexperienced rider, this horse always acts up . [c. 1900]
-
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.
“What makes a horse act up? Fear, mostly,” said Hollywood horse stunt coordinator Ryan Sturz.
From Los Angeles Times ● Feb. 10, 2026
In her four-star review Midgley suggested the show occasionally "feels scripted", noting the Furys know that "the cameras are on them and perhaps act up for them".
From BBC ● Aug. 18, 2023
Keep this smoke-and-mirrors act up, Martin St. Louis’ over-performing bunch can kiss Connor Bedard goodbye.
From Seattle Times ● Oct. 21, 2022
My granddaughters get upset, act up and give her a hard time, and I can understand why.
From Washington Post ● Aug. 31, 2022
He planned to keep the Prince Charming act up all night.
From "Legendary Frybread Drive-In" by Cynthia Leitich Smith
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.
