zero hour

noun
|Updated on: 24 Jul 2018

Definition of zero hour

1 a : 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

Examples of zero hour in a Sentence

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

Recent Examples of zero hour from the Web

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.

Origin and Etymology of zero hour

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


ZERO HOUR Defined for English Language Learners

zero hour

Definition of zero hour for English Language Learners

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



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