undo.
To reverse the effects of an action.
Meaning & usage
To reverse the effects of an action.
Fortunately, we can undo most of the damage to the system by the war.
What's done can't be undone.
To unfasten.
Could you undo my buckle for me?
To unfasten the clothing of (a person).
To impoverish or ruin, as in reputation; to cause the downfall of.
Where this word comes from
From Middle English undōn, from Old English ondōn, from Proto-West Germanic *andadōn (“to undo”), equivalent to un- + do. Cognate with West Frisian ûndwaan, ûntdwaan (“to undo; rid”), Dutch ontdoen (“to undo”).
An operation that reverses a previous action.
How many undos does this program support?
Where this word comes from
From Middle English undōn, from Old English ondōn, from Proto-West Germanic *andadōn (“to undo”), equivalent to un- + do. Cognate with West Frisian ûndwaan, ûntdwaan (“to undo; rid”), Dutch ontdoen (“to undo”).
Misspelling of undue.
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Definitions, grammatical labels, IPA, etymology and examples: Wiktionary contributors, extracted by Kaikki / Wiktextract. Adapted under CC BY-SA 4.0. Selected fields and authored examples are shown; third-party quotations and audio are omitted. See contributor history.
Last enriched 2026-09-10. Definitions are in English. Romanizations are shown when supplied by the source; syllable estimates are omitted for unsupported scripts.