undo
Americanverb (used with object)
-
undoes,
present (3rd person singular)
-
undid,
past
-
undone,
past participle
-
undoing
present participle
-
to reverse the doing of; cause to be as if never done.
Murder once done can never be undone.
-
to do away with; erase; efface.
to undo the havoc done by the storm.
-
to bring to ruin or disaster; destroy.
In the end his lies undid him.
-
to unfasten by releasing.
to undo a gate; to undo a button.
-
to untie or loose (a knot, rope, etc.).
-
to open (a package, wrapping, etc.).
-
Archaic. to explain; interpret.
verb
-
(also intr) to untie, unwrap, or open or become untied, unwrapped, etc
-
to reverse the effects of
-
to cause the downfall of
-
obsolete to explain or solve
Other Word Forms
Derived Forms
Inflected Forms
Participles
Conjugated Forms
Present
-
undosimple
-
undoessimple
-
have undoneperfect
-
has undoneperfect
-
am undoingprogressive
-
are undoingprogressive
-
is undoingprogressive
-
have been undoingperfect progressive
-
has been undoingperfect progressive
Past
-
undidsimple
-
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
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
Commonly Confused Words, List 5
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
Commonly Confused Words, List 11
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
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:
Users of Chinese open-source models can tweak the models to bypass most censorship, though some say they can’t fully undo the influence of biases built into the training data.
From The Wall Street Journal ● Jul. 18, 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
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
And the Ashes humiliation should not, and does not, undo everything that she leaves behind.
From BBC ● Jul. 12, 2026
The bowline had been pulled tight by the strain on it during the night, but by working it back and forth, Malcolm was able to undo it.
From "The Book of Dust: La Belle Sauvage" by Philip Pullman
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 decision by an 11-judge 9th Circuit panel undoes one made last year by a three-judge panel of the same court.
From Los Angeles Times ● Jun. 10, 2024
It undoes the investigation the state's attorney's office did for a year.
From Salon ● Apr. 5, 2023
His fingers shake as he undoes the ties in the wall.
From "The Night Circus" by Erin Morgenstern
Pamela Price was recalled in 2024 and replaced by Ursula Jones Dickson, who quickly undid many of Price’s signature policies.
From Los Angeles Times ● May 29, 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
Unlike the long-ago transition to the cloud, which undid many existing software firms, incumbents aren’t being complacent this time around.
From Barron's ● Mar. 13, 2026
On Monday, the board undid two mistakes that should never have been made.
From BBC ● Jan. 5, 2026
He undid the laces of her shoe and eased it off.
From "Jazz" by Toni Morrison
After years of success that inspired one podcaster to nickname Aschenbrenner the “Nostradamus of AI,” Situational Awareness was undone by forces outside of his tightknit universe.
From The Wall Street Journal ● Aug. 26, 2026
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
"All of the things that it stipulated have now been undone."
From BBC ● Jul. 14, 2026
She did her best, she asked advice of Mrs. Cornelius, she racked her brain to remember what Hannah did that she left undone, she reboiled, resugared, and restrained, but that dreadful stuff wouldn’t ‘jell’.
From "Little Women" by Louisa May Alcott
The appellate panel voiced serious doubts about undoing the consent decree at oral arguments in June.
From Los Angeles Times ● Aug. 19, 2026
But the success of the scheme has also been its undoing – it's growing rapidly and costing the government too much.
From BBC ● Aug. 12, 2026
Instead of taking pleasure in the Witch’s undoing, Sophie tenderly cares for her.
From Salon ● Aug. 4, 2026
“Try again,” my instructor said, after undoing my mess.
From The Wall Street Journal ● Jul. 5, 2026
Once you jump off a cliff, there’s no undoing it, there’s no stopping midair.
From "They Both Die at the End" by Adam Silvera
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.
