Definition of undo in English:

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Pronunciation: /ˌənˈdo͞o/

verb (undoes /-ˈdəz/, undoing; past undid; past participle undone)

[with object]
1Unfasten, untie, or loosen (something): the knot was difficult to undo
More example sentences
  • She noticed that not one of the men had loosened his tie and undone the top shirt button.
  • It was with a sense of the inevitable that I undid the ribbons, loosened the neck and let it slip down over my arms to the ground.
  • He had already slung his jacket and hat on to his bed and now he loosened his tie and undid the top two buttons of his dress shirt.
unlock, unbolt;
loosen, disentangle, extricate, release, detach, free, open;
2Cancel or reverse the effects or results of (a previous action or measure): there wasn’t any way Evelyn could undo the damage
More example sentences
  • The Democrats are strongly opposed to the measures that undo many of the agreements that were struck during the original diesel package in 1999.
  • But this time, it has more to do with rectifying or even undoing some of the damage that resulted from the last international economic movement.
  • Their work may be undone as a result of the popular will.
2.1Cancel (the last one or more commands executed by a computer).
Example sentences
  • These range from nice functions like undoing and redoing a command, running spellcheck and printing a document.
  • Repeating the u command undoes each step in turn; the Ctrl-R keystroke puts them back (redo).
  • We undo the Ctrl-J with Ctrl-Shift - (that's Control-Shift-Hyphen) and type in the semicolon.
3 formal Cause the downfall or ruin of: Iago’s hatred of women undoes him
More example sentences
  • The Minstermen were neat and tidy in possession but, as has been the case on so many occasions this season, were undone by their final ball.
  • Perhaps all those rejections and ringing phones had undone him.
  • He was undone by a limited imagination and a moment of genius.
ruin, undermine, subvert, overturn, scotch, sabotage, spoil, impair, mar, destroy, wreck, eradicate, obliterate;
cancel out, neutralize, thwart, foil, frustrate, hamper, hinder, obstruct
informal blow, put the kibosh on, foul up, scuttle


A feature of a computer program that allows a user to cancel or reverse the last one or more commands executed.
Example sentences
  • However Dreamweaver has really gone to town on this feature making it extremely easy to use, it allows users a virtually unlimited number of number of undos.
  • And the time they save in avoiding undos is invaluable.
  • Graphic designers love to hear that they can revert to any previous version of a document by using the undo feature in the web-based management interface.


Old English undōn (see un-2, do1).

For editors and proofreaders

Syllabification: un·do

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