undo
Americanverb (used with object)
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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
- undoable adjective
- undoer noun
Etymology
Origin of undo
First recorded before 900; Middle English; Old English undōn; cognate with Dutch ontdoen; un- 2, do 1
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.
Justice Elena Kagan said the administration was seeking to undo a legal tradition of birthright citizenship that dates back to English common law.
From BBC • Apr. 1, 2026
Nothing will ever undo the original sin, and devoting your life to ruining someone else’s is a loss for both of you.
From Los Angeles Times • Mar. 19, 2026
"And so those two things combined would make me undo what I did in December," Miran said.
From Barron's • Feb. 19, 2026
“And so those two things combined would make me undo what I did in December.”
From The Wall Street Journal • Feb. 19, 2026
“I sincerely hope you’ll undo this curse you’ve put on us Ashtons. I do appreciate your consideration, what?”
From "The Long-Lost Home" by Maryrose Wood
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.
