undo
Americanverb (used with object)
-
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
Conjugated Forms
Present
-
has undoneperfect 3rd person singular
-
have undoneperfect
-
have been undoingperfect progressive
-
am undoingprogressive 1st person singular
-
is undoingprogressive 3rd person singular
-
has been undoingperfect progressive 3rd person singular
-
are undoingprogressive
-
undoingparticiple
-
undoessingular 3rd person
Past
-
had undoneperfect
-
had been undoingperfect progressive
-
were undoingprogressive plural
-
undidsimple
-
was undoingprogressive singular
-
undoneparticiple
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.
A people who lack the ability to name what was done to them cannot fully organize to undo it.
From Salon • May 31, 2026
And it is black-letter constitutional law that the executive cannot undo such judgments.
From Slate • May 26, 2026
While creditors cannot make claims on an irrevocable trust, JDKatz adds that the court could undo your transfer to a trust.
From MarketWatch • May 23, 2026
But the decline has also stoked concerns over a broader tech pullback over the coming weeks that could undo the S&P 500’s searing spring comeback and set markets back heading into the summer months.
From Barron's • May 18, 2026
“I’m going to undo the tarpaulin,” he said.
From "The Book of Dust: La Belle Sauvage" by Philip Pullman
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.
