un·​do | \ ˌən-ˈdü How to pronounce undo (audio) , ˈən-\
undid\ ˌən-​ˈdid How to pronounce undid (audio) , ˈən-​ \; undone\ ˌən-​ˈdən How to pronounce undone (audio) , ˈən-​ \; undoing\ ˌən-​ˈdü-​iŋ How to pronounce undoing (audio) , ˈən-​ \

Definition of undo

transitive verb

1 : to open or loose by releasing a fastening
2 : to make of no effect or as if not done : make null : reverse
3a : to ruin the worldly means, reputation, or hopes of a politician undone by scandal
b : to disturb the composure of : upset she's come undone

intransitive verb

: to come open or apart

Keep scrolling for more

Other Words from undo

undoer \ ˌən-​ˈdü-​ər How to pronounce undoer (audio) , ˈən-​ \ noun

Synonyms & Antonyms for undo



Visit the Thesaurus for More 

Examples of undo in a Sentence

You can't undo the past. The damage cannot be undone. He was undone by greed.
See More
Recent Examples on the Web By the time Morris backed out, the Bertans trade could not be undone. Jeff Mcdonald, ExpressNews.com, "For Davis Bertans, San Antonio is still home," 25 Oct. 2019 The hosts were undone from another set-piece routine with ten minutes left to play, however, as Bryan Acosta arrived at the back post to nod home and take the game to extra-time. SI.com, "MLS Playoffs Roundup: Rooney Endures Dismal Send Off & Seattle Sounders Sneak Through," 20 Oct. 2019 Those policies could permanently undo the anti-regulatory crusade waged 40 years ago by Mrs. Thatcher, cementing high-tax, pro-workforce rules. Benjamin Mueller, New York Times, "Jeremy Corbyn or No-Deal Brexit? The U.K. Might Have to Choose," 6 Oct. 2019 Six turnovers undid the Gators and gave Nix’s dad a chance to be the hero. Edgar Thompson, orlandosentinel.com, "Auburn QB Bo Nix looks to follow in father’s footsteps against Gators in Swamp," 29 Sep. 2019 Environmental groups caution the change could undo years of work to save the bluefin, which sell for huge sums. San Diego Union-Tribune, "As bluefin recover, a new fight about how to fish for them," 25 Sep. 2019 Acting impulsively or overreacting could quickly undo a great deal of progress. Tribune Content Agency, oregonlive.com, "Horoscope for June 25, 2019: Pisces, your past has given you wisdom and grit; Aquarius, march to your own beat," 25 June 2019 The rollback of the 2015 measure, known as the Waters of the United States rule, adds to a long list of environmental rules the administration has worked to weaken or undo in the past 2½ years. BostonGlobe.com, "Trump administration will repeal a key Obama-era clean water rule - The Boston Globe," 13 Sep. 2019 For starters, the NCAA would not sit by idly while California attempts to undo decades of NCAA policy. Michael Mccann, SI.com, "What Will Happen If the California 'Fair Pay to Play Act' Gets Signed Into Law?," 10 Sep. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'undo.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of undo

before the 12th century, in the meaning defined at transitive sense 1

Keep scrolling for more

Learn More about undo

Time Traveler for undo

Time Traveler

The first known use of undo was before the 12th century

See more words from the same century

Statistics for undo

Last Updated

18 Nov 2019

Cite this Entry

“Undo.” The Merriam-Webster.com Dictionary, Merriam-Webster Inc., https://www.merriam-webster.com/dictionary/undoes. Accessed 21 November 2019.

Keep scrolling for more

More Definitions for undo


How to pronounce undo (audio)

English Language Learners Definition of undo

: to open or release (something) : to unfasten or loosen (something)
: to change or stop the effect of (something)
formal : to cause the failure of (someone or something)


un·​do | \ ˌən-ˈdü How to pronounce undo (audio) \
undid\ -​ˈdid \; undone\ -​ˈdən \; undoing\ -​ˈdü-​iŋ \; undoes\ -​ˈdəz \

Kids Definition of undo

1 : untie sense 2, unfasten Can you undo this knot?
2 : to cancel the effect of : reverse The damage cannot be undone.
3 : to cause the ruin or failure of He was undone by greed.

Keep scrolling for more

More from Merriam-Webster on undo

Thesaurus: All synonyms and antonyms for undo

Rhyming Dictionary: Words that rhyme with undo

Spanish Central: Translation of undo

Nglish: Translation of undo for Spanish Speakers

Britannica English: Translation of undo for Arabic Speakers

Comments on undo

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


strength of mind

Get Word of the Day daily email!

Test Your Vocabulary

Name that Food Quiz

Spell It

Can you spell these 10 commonly misspelled words?


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

Love words? Need even more definitions?

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