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
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.
Appeared in the April 9, 2026, print edition as 'Truce Can’t Undo Region’s Energy Hangover'.
From The Wall Street Journal • Apr. 8, 2026
Undo the tight, slicked back bun and bring in halo dyed hair, dark eyeliner and the piercing she did herself on the inside of her upper lip.
From Los Angeles Times • Feb. 5, 2026
Grid View The Undo Send at the bottom of the screen lets you change your mind — if your recipient also has iOS 16.
From The Verge • Sep. 10, 2022
Shaking your phone will display an Undo Typing window with the option to Undo.
From Fox News • Jan. 27, 2022
“Put your hair in the front like this in the portrait. Undo the braids and leave it loose. A woman’s hair is her greatest adornment, a way to present femininity without being immodest.”
From "The Red Car to Hollywood" by Jennie Liu
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.
