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

Updates to the system mitigate this danger by relying on multiple sensors, limiting the number of times the system can engage, and preventing the system's corrections from being so extreme that they could not be undone by pilots. Eric Limer, Popular Mechanics, "Lion Air Pilots Had Less Than a Minute to Avert Fatal Crash," 27 Mar. 2019 President Trump has sought to undo the very protections and innovations that are helping millions of students receive a better education. WSJ, "Democrats Really Do Own Education Reform," 20 Mar. 2019 Drew Peterson is taking his case to the nation’s highest court as the former Bolingbrook police officer seeks to undo his murder conviction for the death of his third wife. William Lee, chicagotribune.com, "Drew Peterson asks U.S. Supreme Court to hear appeal of murder conviction of 3rd wife," 18 June 2018 The Trump Administration has sought to undo Barack Obama’s legacy on climate change at every turn — from withdrawing from the Paris Agreement to scrapping EPA regulations — arguing that addressing global warming hurts American industry. Justin Worland, Time, "Big Business Wants to Stop Trump From Leaving This Other Climate Deal," 3 May 2018 Newsom is touting his role in creating the universal health care program in the campaign, as Republicans seek to undo Obamacare and California considers its own path. Angela Hart, sacbee, "Will California fail financially without single-payer health care? Candidates for governor disagree | The Sacramento Bee," 24 Apr. 2018 Votes cannot undo immigration policy in one fell swoop, but votes can elect a new Congress with the oversight to uncover and establish the truth. Marie Claire, "Why Your Vote Is More Important This Year Than Ever Before," 16 Oct. 2018 While Lula’s conviction is purportedly about fighting corruption and impunity, it, in fact, aims to teach the poor a lesson: the presidential legacy of a mixed-race worker, with little formal education, will be undone by the country’s elites.... Monitor Editors, The Christian Science Monitor, "The US and its allies knocked Russia off balance, Pleading for a de-escalation of the US-China trade war, The jailing of ‘Lula’ reveals unequal treatment of corrupt politicians, US postwar management of Iraq has been a disaster, Learn from life mistakes," 21 Apr. 2018 This rule applies across the board, to all aspects of the government, and in all corners of the land: If Barack Obama did it, it must be undone. Charles P. Pierce, Esquire, "Trump's USDA Believes That Factory Farmed Animals Have It Too Good," 13 Mar. 2018

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

8 Apr 2019

Look-up Popularity

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

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