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zero hour

noun

Simple Definition of zero hour

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

Source: Merriam-Webster's Learner's Dictionary

Full Definition of zero hour

  1. 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. 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>



Origin of zero hour

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


First Known Use: 1915


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