undo

verb

un·​do ˌən-ˈdü 

ˈən-

undid ˌən-ˈdid 

ˈən-

; undone ˌən-ˈdən 

ˈən-

; undoing ˌən-ˈdü-iŋ 

ˈən-

; undoes

ˌən-ˈdəz, 

ˈən-

transitive verb

1

: to open or loosen by releasing a fastening

undid her jacket

2

: to make of no effect or as if not done : make null : reverse

The damage cannot be undone.

3

a

: to ruin the worldly means, reputation, or hopes of

a politician undone by scandal

b

: to disturb the composure of : upset

she's come undone

c

: seduce sense 3

intransitive verb

: to come open or apart

undoer

ˌən-ˈdü-ər 

ˈən-

noun

Synonyms of undo

• paralyze
• scare
• frighten
• intimidate

Examples of undo in a Sentence

You can't undo the past.

The damage cannot be undone.

He was undone by greed.

Recent Examples on the Web

Americans want to undo the Citizens United ruling, according to Tom Moore, a former Federal Elections Commission lawyer who is now a senior fellow at the Center for American Progress. —ABC News, 12 May 2026

Errors undid the Mets on Sunday in the desert as well. —Abbey Mastracco, New York Daily News, 11 May 2026

The hard work is going to be undoing centuries of religious, epistemic, political, and cultural erasure, and that’s up to humans. —Anne Doran, ARTnews.com, 11 May 2026

If that happens, the economist warned that the retail sector might undo some of its recent labor force expansion to account for sliding demand. —Alex Harring, CNBC, 10 May 2026

Word History

First Known Use

before the 12th century, in the meaning defined at transitive sense 1

Rhymes for undo

• accrue
• ado
• ainu
• aircrew
• airscrew
• anew
• askew
• baboo
• babu
• bamboo
• beaucoup
• bijou

Kids Definition

undo

verb

un·​do ˌən-ˈdü 

ˈən-

undid -ˈdid  ; undone -ˈdən  ; undoing -ˈdü-iŋ 

1

: to make or become unfastened or loosened : open, untie

undo a knot

2

: to destroy the effect of : nullify, reverse

3

a

: to cause the ruin of

your stubbornness undid you

undone by greed

b

: to disturb the calmness of : upset

she's come undone

undoer noun