act up

verb

Definition of act up 

(Entry 1 of 2)

intransitive verb

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

ACT UP

abbreviation

Definition of ACT UP (Entry 2 of 2)

AIDS Coalition to Unleash Power

Keep scrolling for more

Synonyms for act up

Synonyms: Verb

act out, carry on, misbehave

Visit the Thesaurus for More 

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

First Known Use of act up

Verb

1879, in the meaning defined at sense 1

Keep scrolling for more

Learn More about act up

Dictionary Entries near act up

actuate

actuator

ACT UP

act up

actus

acu-

ACU

Statistics for act up

Look-up Popularity

Time Traveler for act up

The first known use of act up was in 1879

See more words from the same year

More from Merriam-Webster on act up

See words that rhyme with act up

Thesaurus: All synonyms and antonyms for act up

Comments on act up

What made you want to look up act up? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

occurring twice a year or every two years

Get Word of the Day daily email!

Test Your Vocabulary

Name that Food Quiz

True or False

Test your knowledge - and maybe learn something along the way.

TAKE THE QUIZ
Add Diction

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!