Wiktionary
vb. (present participle of act up English)
Usage examples of "acting up".
And they didn't bother to check in on a secure line unless there was something going on they didn't want the listeners to know about, which meant it was either something sensitive like one of the town fathers acting up, or something personal.
His leg was obviously acting up tonight, she speculated, and when Colin propped his foot up on the cushion next to her, she knew her guess was right.
Yet every time she walked into his office, Kris Gavin brought memories of his younger days-days when vitality meant more than getting through twenty-four hours without his ulcer acting up.
I thought so, since you had shields all over him, but that could have just meant Miri's paranoia was acting up.
That my great grandfather was in the diplomatic corps over there in France when the communists were acting up back in the eighteen forties and maybe I could tell him a little about my grandfather's second marriage?