zero hour

noun

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

Synonyms

• boiling point
• breaking point
• clutch
• conjuncture
• crisis
• crossroad(s)
• crunch
• crunch time
• Dunkirk
• emergency
• exigency
• extremity
• flash point
• head
• juncture
• tinderbox

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

Fighting, however, continued up to the zero hour, with Israeli airstrikes in Lebanon far into the night. —Scott Neuman, NPR, 27 Nov. 2024

English learners can attend a specialized class for learning to speak and write can be accomplished with a before-school (zero hour) or after-school period. —Madeleine Parrish, The Arizona Republic, 8 Oct. 2024

As the zero hour approached, the men fiddled with their automatic rifles while their leader, Habib Rahman Inqayad, scrambled to get the exact location of their target. —Safiullah Padshah, New York Times, 17 June 2023

The Germans called 1945 Stunde null, zero hour. —The New Yorker, 4 July 2021

This point of the Vernal Equinox on the celestial equator defines the zero hour of R.A. in our coordinate system. —Curtis Roelle, baltimoresun.com/maryland/carroll, 6 Mar. 2021

As Pac-12 teams prepare for Week Two, the existential clock approaches zero hour. —oregonlive, 8 Sep. 2022

Hiking through the emerald green canopy of the bosque, or riverside cottonwood forest, near downtown Albuquerque, Tricia Snyder, an advocate for WildEarth Guardians, believes zero hour has arrived for the Rio Grande. —Jim Robbins, Wired, 25 June 2022

Biden's August deadline marks zero hour for the next phase of a larger international quest: to trace back the virus in order to hold the responsible parties to account, and to understand its inception in order to prevent the next one. —Sasha Pezenik, ABC News, 25 Aug. 2021

Word History

Etymology

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

First Known Use

1915, in the meaning defined at sense 1a

Rhymes for zero hour

• airpower
• brainpower
• devour
• empower
• firepower
• horsepower
• manpower
• mayflower
• safflower
• sunflower
• wallflower
• watchtower

Kids Definition

zero hour

noun

1

: the hour at which a military action is scheduled to start

2

: a moment of crisis