zero hour

noun

Definition of zero hour

1a : the hour at which a planned military operation is scheduled to start
b : the time at which a usually significant or notable event is scheduled to take place
2 : a time when a vital decision or decisive change must be made

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Examples of zero hour in a Sentence

we're at the zero hour, so someone has to make a decision

Recent Examples on the Web

Major milestones in the emergency plan are performed according to a predetermined schedule in the hours and days leading up to the zero hour. Daniel B. Hess, CNN, "How do hospitals prepare for hurricanes?," 2 Sep. 2019 Major milestones in the emergency plan are performed according to a predetermined schedule in the hours and days leading up to the zero hour. Daniel B. Hess, Quartz, "How Florida hospitals are getting ready for Hurricane Dorian," 30 Aug. 2019 In Act Two, tensions continue to rise and reach their frightful climax at zero hour detonation. Paul Ross, Popular Mechanics, "I Am Become Opera: An Atomic Show In the Shadow of Los Alamos," 27 July 2018 His business partner Robert Goldfarb then served as the unpaid trustee for a few years, spending zero hours a week on foundation business, according to tax filings. Andrea Fuller, WSJ, "Private Charitable Foundations Give Lavish Rewards to Insiders," 29 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'zero hour.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of zero hour

1915, in the meaning defined at sense 1a

History and Etymology for zero hour

from its being marked by the count of zero in a countdown

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Statistics for zero hour

Last Updated

18 Sep 2019

Look-up Popularity

Time Traveler for zero hour

The first known use of zero hour was in 1915

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More Definitions for zero hour

zero hour

noun

English Language Learners Definition of zero hour

: the time at which an event (such as a military attack) is scheduled to begin

More from Merriam-Webster on zero hour

Rhyming Dictionary: Words that rhyme with zero hour

Thesaurus: All synonyms and antonyms for zero hour

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