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

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Other Words from undo

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

Synonyms & Antonyms for undo


demoralize, emasculate, paralyze, unman, unnerve, unstring



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Examples of undo in a Sentence

You can't undo the past. The damage cannot be undone. He was undone by greed.
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Recent Examples on the Web

The administration, undoing decades of environmental protections in the 19-million acre refuge, plans to sell drilling leases in a part of it known as the 1002 Area, which is 1.5 million acres of the coastal plain by the Beaufort Sea. New York Times, "Arctic Refuge Likely Won’t Be Surveyed Before Oil Lease Sales," 8 July 2019 No treaty could have undone the psychological damage the German leadership inflicted upon its own citizens. Joseph Loconte, WSJ, "The Versailles Treaty Gets a Bum Rap," 27 June 2019 In this way, the proliferation of bogus medical science in the Internet age resembles a public-health crisis: The harm can be hard to calculate, and remedies cannot undo the damage already done. Abby Ohlheiser, Washington Post, "They turn to Facebook and YouTube to find a cure for cancer — and get sucked into a world of bogus medicine," 25 June 2019 President Barack Obama's administration had moved to strip it of its powers to OK school programs, but following a legal battle, President Donald Trump's administration undid that move. Chris Quintana, USA TODAY, "A worthless degree? Betsy DeVos wants to change rules for which colleges stay open, close," 21 June 2019 The remedy is to remove all the damaged fruits because the damage can't be undone. oregonlive.com, "Ask an Expert: Remove sunburned plums now for a better harvest later," 28 June 2019 Once again the Eagles were undone by a late strike, as Nemanja Matic struck in added time to secure a 3-2 victory for the Red Devils. SI.com, "Aaron Wan-Bissaka: 5 Things to Know About the Starlet Ahead of His £50m Manchester United Move," 27 June 2019 Sure, ant-mageddon might be undone with a lemony rag, why not. Michelle Santiago Cortés, refinery29.com, "A Nightmare Infestation On A Plane Journey Told In Tweets," 17 June 2019 Much of Obama’s legacy, lacking the force of congressional action, has been undone by Trump. Tal Kopan, SFChronicle.com, "Kamala Harris would lean on presidential power, not Congress, for big plans," 15 June 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.

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First Known Use of undo

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

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Statistics for undo

Last Updated

15 Jul 2019

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Time Traveler for undo

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

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More Definitions for undo



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.

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More from Merriam-Webster on undo

Rhyming Dictionary: Words that rhyme with undo

Thesaurus: All synonyms and antonyms for undo

Spanish Central: Translation of undo

Nglish: Translation of undo for Spanish Speakers

Britannica English: Translation of undo for Arabic Speakers

Comments on undo

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