Definition of undo verb from the Oxford Advanced Learner's Dictionary

      

    undo

     verb
    verb
    BrE BrE//ʌnˈduː//
     
    ; NAmE NAmE//ʌnˈduː//
     
    Verb Forms present simple I / you / we / they undo
    BrE BrE//ʌnˈduː//
     
    ; NAmE NAmE//ʌnˈduː//
     
    he / she / it undoes
    BrE BrE//ʌnˈdʌz//
     
    ; NAmE NAmE//ʌnˈdʌz//
     
    past simple undid
    BrE BrE//ʌnˈdɪd//
     
    ; NAmE NAmE//ʌnˈdɪd//
     
    past participle undone
    BrE BrE//ʌnˈdʌn//
     
    ; NAmE NAmE//ʌnˈdʌn//
     
    -ing form undoing
    BrE BrE//ʌnˈduːɪŋ//
     
    ; NAmE NAmE//ʌnˈduːɪŋ//
     
     
    jump to other results
  1. 1  undo something to open something that is fastened, tied or wrapped to undo a button/knot/zip, etc. to undo a jacket/shirt, etc. I undid the package and took out the books. opposite do somethingup
  2. 2undo something to cancel the effect of something He undid most of the good work of the previous manager. It's not too late to try and undo some of the damage. UNDO (= a command on a computer that cancels the previous action)
  3. 3[usually passive] undo somebody/something (formal) to make somebody/something fail The team was undone by the speed and strength of their opponents.
  4. Word Origin Old English undōn (see un-, do1).Extra examples He undid his jacket and threw it over a chair. I can’t undo this zip—it seems to be stuck. It’s not too late to try and undo some of the damage. Just select ‘Edit’ and ‘Undo’ to cancel the previous action. to undo the damage/​harm/​errors to undo the good work/​years of endeavour/​reforms
See the Oxford Advanced American Dictionary entry: undo