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.
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
Just last month, a superior court judge in Santa Barbara County said prior intervention by the federal government wasn’t enough to undo an earlier order that kept the pipeline shut down.
From Barron's • Mar. 14, 2026
She added: "I recognise that any sentence imposed by this court will not undo what has been done, or repair or remove the hurt and grief suffered by them".
From BBC • Mar. 13, 2026
All of the romance and wistfulness of the concert can’t undo years of heartbreak and resentment.
From Salon • Feb. 5, 2026
“I was thinking,” said Malcolm, “about these screws, right. You know when the slot gets worn away, it’s much harder to undo, because the screwdriver can’t bite?”
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.
