Definition of act up
1 : to act in a way different from that which is normal or expected: 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>
Examples of act up
<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>
First Known Use of act up
Rhymes with act up
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Definition of ACT UP
AIDS Coalition to Unleash Power
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