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

Synonyms & Antonyms for undo



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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 Some of the harm accumulates over time, so it’s not at all too late to deal with that and undo it. Will Knight, Wired, "The US Needs More Foreign Artificial Intelligence Know-How," 6 Jan. 2021 Trump proved it can be done; the question is, does Biden want to undo the damage and reverse the fortunes of immigrants with as much fervor? Felipe De La Hoz, The New Republic, "Joe Biden Doesn’t Need the GOP’s Permission to Fix Our Broken Immigration System," 25 Dec. 2020 Instead of trying to undo the wise and pragmatic work of the founders, Democrats and their supporters should be thanking them. James Freeman, WSJ, "Obama Wins Another Round Against Community Organizers," 18 Dec. 2020 Although the attorney general typically fights alongside county district attorneys to uphold convictions, Becerra is trying to undo Fagundes’ work. Alex Wigglesworth, Los Angeles Times, "With a woman in prison for a stillbirth, California’s murder law is tested," 16 Dec. 2020 While the Biden administration can undo it, the process will require resources that are sorely needed to take on a biodiversity crisis that has put a million species at risk of extinction around the world. New York Times, "Monarch Butterflies Qualify for Endangered List. They Still Won’t Be Protected.," 15 Dec. 2020 Even if Trump were successful in Wisconsin, the state’s 10 Electoral College votes would not be enough to undo Biden’s overall victory as states around the country certify results. Scott Bauer, Anchorage Daily News, "Wisconsin certifies Joe Biden as winner following recount," 1 Dec. 2020 The new 2021 Toyota Sienna appears to want to undo the stigma that minivans have suffered for decades. Car and Driver, "Tested: 2021 Toyota Sienna Sheds Minivan Stereotypes," 27 Oct. 2020 Fox’s biggest postelection competitors, are seeing their audiences grow at a rapid clip—and seem poised to hold on to them even after Trump’s pathetic efforts to undo the 2020 election end. Alex Shephard, The New Republic, "Fox News Is in Trouble," 10 Dec. 2020

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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Time Traveler for undo

Time Traveler

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

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Statistics for undo

Last Updated

14 Jan 2021

Cite this Entry

“Undo.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/undo. Accessed 22 Jan. 2021.

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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.

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