Definition of undo in US English:



[with object]
  • 1Unfasten, untie, or loosen (something)

    ‘the knot was difficult to undo’
    • ‘She noticed that not one of the men had loosened his tie and undone the top shirt button.’
    • ‘She undid the string and unwrapped a silk scarf, covered with flowers in varying shades of pink.’
    • ‘As he passed through the doorway and entered the vestibule, he carelessly tossed his hat to the coat rack beside the door and then proceeded to loosen his cravat and undo the buttons of his jacket.’
    • ‘And when she finally had it open, she undid the folded slip and started reading.’
    • ‘She unlocked the deadbolt, undid the chain, and opened the door.’
    • ‘She opened her door and undid her seatbelt, not intending to say anything more.’
    • ‘The young captain then undid her safety harness, stood up, and stretched.’
    • ‘I lay there with my shirt open and watched him undo his belt, then stand up letting his pants fall.’
    • ‘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.’
    • ‘Together we undid my trousers and unwrapped the bandage and there it was.’
    • ‘Sitting outside a pub in the Scottish border town of Yetholm on a sunny summer evening, I reach down, undo my laces and release my feet from inside my walking boots.’
    • ‘Shooing the flies away, he undid the knot and unwrapped it.’
    • ‘Grabbing one, I tossed it on the floor and undid my pants, opening a drawer to find the red toothbrush I kept there.’
    • ‘She saw him smile and he undid the locks and opened the door, blocking her view of both men.’
    • ‘He undid the loose shirt he wore and showed her the angry red scars of the recently healed wounds and the dressings that still covered the deeper wounds.’
    • ‘He had loosened his tie and undone a couple of buttons down to his chest.’
    • ‘Brett opened the door, undoing her seatbelt and picking her up in his arms.’
    • ‘John undid the latch and opened the door as if he were breaking in, using his shoulder like a battering ram.’
    • ‘He loosened his tie and undid the first button of his collar so he wouldn't suffocate.’
    • ‘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.’
    unfasten, unbutton, unhook, untie, unlace
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  • 2Cancel or reverse the effects or results of (a previous action or measure)

    ‘there wasn't any way Evelyn could undo the damage’
    • ‘To date, nothing has been discovered to undo the previous UVR damage to the skin.’
    • ‘But there is a lot of damage to be undone, a lot of low-income families in serious debt, and the package focuses on rewarding those children with parents in work.’
    • ‘After erasing the logo I could see her clearly, but it took a while for her to be convinced that the damage had been undone.’
    • ‘Even the most effective memory enhancer can't undo the damage resulting from a careless lifestyle or uncontrolled medical conditions.’
    • ‘One solution is to seek experiences that could undo or reverse the patterns of experience that could have created the unwanted preference.’
    • ‘Another benefit is that any spell can be un-cast, any effect can be undone.’
    • ‘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 I am delighted to know that Hollywood, of all places, has now undone much of the damage.’
    • ‘Now they are trying to undo some of the damage at the very last minute, with rushed legislation.’
    • ‘Mr Foxman accepted the apology, but many predict it will be difficult to undo the damage.’
    • ‘The act can never be undone; the damage to the victim is residual and permanent.’
    • ‘Even if Labour lost the referendum, there would be time for the damage to be undone before the 2005 general election.’
    • ‘Once a course of action is settled on it is so difficult to undo the momentum of the action and its direction.’
    • ‘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.’
    • ‘As for the Johnson brothers, the damage can never be undone.’
    • ‘Their work may be undone as a result of the popular will.’
    • ‘No matter how many millions of pounds are spent on Blackburn town centre the damage cannot be undone and the shopkeepers are paying the price in loss of trade.’
    • ‘Your father's success in foreign policy was quickly undone by discontent on domestic policies and a bad economy.’
    • ‘It will be difficult or impossible to undo the damage by means of a retrospective external inquiry.’
    • ‘The Indian government team lost a lot of ground and successive efforts were devoted to undoing some of this damage.’
    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
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    1. 2.1 Cancel (the last one or more commands executed by a computer).
      • ‘An undo function permits users to undo the most recent configuration.’
      • ‘We undo the Ctrl-J with Ctrl-Shift - (that's Control-Shift-Hyphen) and type in the semicolon.’
      • ‘When the changes are complete, it presents you with a list of changes and gives you the option to undo any of them, if necessary.’
      • ‘Repeating the u command undoes each step in turn; the Ctrl-R keystroke puts them back (redo).’
      • ‘These range from nice functions like undoing and redoing a command, running spellcheck and printing a document.’
  • 3formal Cause the downfall or ruin of.

    ‘Iago's hatred of women undoes him’
    • ‘He was undone by a limited imagination and a moment of genius.’
    • ‘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.’
    • ‘It was his craving for status that was eventually to help undo him.’
    • ‘He was undone by a lack of sound financial resources and divided political control.’
    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
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  • A feature of a computer program that allows a user to cancel or reverse the last one or more commands executed.

    • ‘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.’
    • ‘Click on the undo tab on the top right of the DTML editing screen, and select the version to which you want to return.’
    • ‘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.’
    • ‘And the time they save in avoiding undos is invaluable.’
    • ‘I think it's the lack of undo function that makes it so frustrating.’


Old English undōn (see un-, do).