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

• demoralize
• emasculate
• paralyze
• unman
• unnerve
• unstring

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

But undoing the observation and the observer’s recollection of it is the only way to take the system back to its initial conditions and thereby retrieve Charlie’s qubit in its original, unmeasured state. —Anil Ananthaswamy, Scientific American, 25 June 2024

Fans have been bombarding social media accounts for Bridgerton as well as the actors, demanding that the show undo the casting of Baduza. —Aja Romano, Vox, 18 June 2024

The state’s team of investigators and prosecutors assembled about a year and a half ago to examine efforts to undo or undermine Trump’s 10,457-vote loss in the state. —Yvonne Wingett Sanchez, Washington Post, 18 June 2024

Which led to conservative folks seizing on our anxieties to undo criminal justice reform. —Anita Chabria, Los Angeles Times, 13 June 2024

Word History

First Known Use

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

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