[ uhn-doo ]
See synonyms for: undoundidundoingundone on Thesaurus.com

verb (used with object),un·did [uhn-did], /ʌnˈdɪd/, un·done [uhn-duhn], /ʌnˈdʌn/, un·do·ing.
  1. to reverse the doing of; cause to be as if never done: Murder once done can never be undone.

  2. to do away with; erase; efface: to undo the havoc done by the storm.

  1. to bring to ruin or disaster; destroy: In the end his lies undid him.

  2. to unfasten by releasing: to undo a gate; to undo a button.

  3. to untie or loose (a knot, rope, etc.).

  4. to open (a package, wrapping, etc.).

  5. Archaic. to explain; interpret.

Origin of undo

First recorded before 900; Middle English; Old English undōn; cognate with Dutch ontdoen; see origin at un-2, do1

Other words from undo

  • un·do·a·ble, adjective

Words that may be confused with undo

Words Nearby undo

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use undo in a sentence

British Dictionary definitions for undo


/ (ʌnˈduː) /

verb-does, -doing, -did or -done (mainly tr)
  1. (also intr) to untie, unwrap, or open or become untied, unwrapped, etc

  2. to reverse the effects of

  1. to cause the downfall of

  2. obsolete to explain or solve

Derived forms of undo

  • undoer, noun

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012