Definition of undo in English:

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Pronunciation: /ʌnˈduː/

verb (undoes, 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.
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.
revoke, overrule, overturn, repeal, rescind, reverse, retract, take back, rule against, disallow, veto, countermand, cancel, annul, nullify, render null and void, invalidate, render invalid, negate, abrogate, disestablish, make ineffective, set aside, do away with, wipe out, bring to an end;
Law  avoid, vacate
archaic recall
rare disannul
2.1Cancel (the last command executed by a computer): you can frequently undo the error if you notice it in time
More 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, put an end to, put at risk, subvert, overturn, topple, scupper, scotch, sabotage, spoil, mess up, make a mess of, quash, squelch, crush, harm, cripple, impair, mar, destroy, devastate, play havoc with, wreck, smash, shatter, annihilate, eradicate, obliterate, defeat;
cancel out, neutralize, render ineffective;
thwart, upset, foil, frustrate, hamper, hinder, obstruct
informal botch, blow, put the kibosh on, foul up, muck up, louse up, blow a hole in, do for
British informal cock up, throw a spanner in the works of
North American informal rain on someone's parade, throw a monkey wrench in the works of
vulgar slang bugger up, fuck up, balls up
archaic bring to naught


A feature of a computer program that allows a user to cancel or reverse the last command executed: [as modifier]: the undo command
More 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

Line breaks: undo

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