undo
Americanverb (used with object)
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undoes,
present (3rd person singular)
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undid,
past
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undone,
past participle
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undoing
present participle
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to reverse the doing of; cause to be as if never done.
Murder once done can never be undone.
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to do away with; erase; efface.
to undo the havoc done by the storm.
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to bring to ruin or disaster; destroy.
In the end his lies undid him.
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to unfasten by releasing.
to undo a gate; to undo a button.
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to untie or loose (a knot, rope, etc.).
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to open (a package, wrapping, etc.).
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Archaic. to explain; interpret.
verb
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(also intr) to untie, unwrap, or open or become untied, unwrapped, etc
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to reverse the effects of
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to cause the downfall of
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obsolete to explain or solve
Other Word Forms
Derived Forms
Inflected Forms
Participles
Conjugated Forms
Present
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undosimple
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undoessimple
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have undoneperfect
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has undoneperfect
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am undoingprogressive
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are undoingprogressive
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is undoingprogressive
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have been undoingperfect progressive
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has been undoingperfect progressive
Past
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undidsimple
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had undoneperfect
-
was undoingprogressive
-
were undoingprogressive
-
had been undoingperfect progressive
Future
Etymology
Origin of undo
First recorded before 900; Middle English; Old English undōn; cognate with Dutch ontdoen; see origin at un- 2, do 1
Explanation
When you undo something, you make it invalid, like when governments undo treaties they've signed in the past. Another way to undo is simply to open: "I couldn't undo the knot on my sneakers, so I just slipped them off." When we undo something, we cancel out its results, or reverse them. You might try to undo the damage caused by your little sister's baseball, offering to replace your neighbor's broken window. Formally, this verb also means "cause downfall or ruin," so you could say, "His love of power will undo him in the end."
Vocabulary lists containing undo
Commonly Confused Words, List 3
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Commonly Confused Words, List 5
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Commonly Confused Words, List 11
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
Their stalemate heated up this summer, when a fresh appeal seeking to undo the agreement reached the 9th Circuit.
From Los Angeles Times ● Aug. 19, 2026
The prophecy states that they’ll acquire the powers of “Break” – to dismantle or undo something – and “Seal” to contain, reconstruct or suppress something.
From Salon ● Jul. 18, 2026
“Many of the hyperscalers are beginning to undo years of carefully manicured capital allocation, with share buybacks now making way for share issues,” says John Lloyd, Janus Henderson’s global head of multisector credit.
From The Wall Street Journal ● Jul. 15, 2026
With Tuesday's lawsuit, one of Hollywood's powerful labor unions hopes to undo the US Department of Justice's approval.
From Barron's ● Jul. 15, 2026
“Does that mean there’s a way to undo the curse without committing—” He glanced at the children and dropped his voice.
From "The Long-Lost Home" by Maryrose Wood
The two-segment operating model undoes changes made by former chief executive Bernard Looney that were initiated as part of BP’s pivot to lower-carbon sources of energy.
From The Wall Street Journal ● Jun. 9, 2026
The decision undoes a ruling by US District Judge Maame E Frimpong in Los Angeles, who had said that there is a "mountain of evidence" showing the raids were violating the US Constitution.
From BBC ● Sep. 8, 2025
The Malibu property, listed at $39 million, is in the midst of renovation as its new owner undoes Ye’s head-scratching remodeling choices.
From Los Angeles Times ● Jul. 3, 2025
But positioning her as Ethan’s maybe-girlfriend — as if in obeisance to and at the same time defiance of some foundational rule of musical theater — undoes that work.
From New York Times ● Feb. 6, 2024
Wordlessly, she reaches up to the nape of her neck and undoes the loose bun she wears when cooking.
From "Internment" by Samira Ahmed
With an ample majority of the 117 members present in the 130-seat chamber, lawmakers undid a rule that since 2020 had limited the president's ability to impose states of emergency.
From Barron's ● May 27, 2026
The Japanese yen surged against the dollar in Asian trade as possible central bank intervention undid the currency’s wartime losses.
From The Wall Street Journal ● May 1, 2026
How did public health backslide so hard that it undid decades of progress—and is there any hope we can get back on track?
From Slate ● Jul. 11, 2025
But within minutes indiscipline undid their hard work once again when flanker Jack O'Donoghue was sin-binned for conceding a penalty try.
From BBC ● Apr. 25, 2025
Xan snatched the child out of the air and undid the transformation.
From "The Girl Who Drank the Moon" by Kelly Barnhill
That era concluded quickly, undone by his hubris and deceit.
From Los Angeles Times ● Aug. 15, 2026
Enthusiasm around artificial intelligence had sent some stocks surging too far, too fast this year — and to some extent, that came undone in July.
From MarketWatch ● Aug. 1, 2026
Ellis' granddaughter Laura Enston said that although the impact of the sentence on her family could not be undone, she felt justice had been done after 70 years.
From BBC ● Jul. 8, 2026
In the early 2000s, England’s so-called Golden Generation was undone by simmering rivalries between the boldface names.
From The Wall Street Journal ● Jun. 17, 2026
The composure I had fifteen minutes ago is coming undone, thread by thread.
From "Girl in the Blue Coat" by Monica Hesse
The appellate panel voiced serious doubts about undoing the consent decree at oral arguments in June.
From Los Angeles Times ● Aug. 19, 2026
In LaSalle’s opinion, echoed by many critics at the time, the maudlin elements of the film’s third act are its undoing.
From Salon ● Jun. 28, 2026
Think of it as undoing all the bad things that sitting does.
From Barron's ● Jun. 27, 2026
The rise of a man known as “The King of the North” could finally be his undoing.
From The Wall Street Journal ● Jun. 20, 2026
Xan tore down the road, her old bones groaning, undoing spell after spell, before she caught up to the wayward girl.
From "The Girl Who Drank the Moon" by Kelly Barnhill
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
