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undo - definition and synonyms


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verb undo pronunciation in American English /ʌnˈdu/
Word Forms
present tense
present participleundoing
past tenseundid
past participleundone
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  1. 1
    [transitive] to open, untie, or remove something so that it no longer closes, fastens, or connects another thing

    He quickly undid the screws that held the lid on.

    I can’t undo my belt.

  2. 2
    [transitive] to have the effect of changing something back into its original, usually worse state

    She warned that one mistake could undo all their achievements.

    1. a.
      [intransitive/transitive] computing to give a computer an instruction to ignore the last change that you made to a document

sea lion

in an online conversation, repeatedly asking a person questions which suggest that you are interested in what they are talking about, but are actually intended to annoy them

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