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

English became a buffer, a soft curtain between myself and the memories that threatened to undo me. —Literary Hub, 6 Nov. 2025

That could be undone, Wisconsin Insurance Commissioner Nathan Houdek said, if the subsidies go back to previous, reduced levels at the end of the year, when increases to the financial aid expire. —Sarah Volpenhein, jsonline.com, 6 Nov. 2025

In a second ruling, McCormick decided that an additional shareholder vote on the compensation package -- even if made with full knowledge of the initial problems surrounding the negotiation of the agreement -- could not undo those problems. —Max Zahn, ABC News, 6 Nov. 2025

Since taking over, Jassy has been trying to undo some of that work. —Gabrielle Fonrouge,annie Palmer,frank Holland, CNBC, 4 Nov. 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