undo

verb

un·​do ˌən-ˈdü 

ˈən-

undid ˌən-ˈdid 

ˈən-

; undone ˌən-ˈdən 

ˈən-

; undoing ˌən-ˈdü-iŋ 

ˈən-

transitive verb

1

: to open or loose by releasing a fastening

2

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

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

• 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

Effectively, this turned the workspace into a yank buffer along with all your documents, and undoing any destructive editing operation thus became merely another cut and paste. —Cameron Kaiser, ArsTechnica, 12 Sep. 2025

Protecting Users From Themselves No matter how sophisticated network defenses are, a careless action can undo them. —Max Silber, Forbes.com, 11 Sep. 2025

Annexation, however, could upend that entire process, undoing past agreements and making future ones impossible. —Yair Rosenberg, The Atlantic, 11 Sep. 2025

When the last clasp was undone, Rusty fell face first to the floor with a great thud. —Manuel Muñoz, Literary Hub, 11 Sep. 2025

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