zero hour

noun

1. the time set for the beginning of a military attack or operation.
2. the time set for the beginning of any event or action.
3. a decisive or critical time.

zero hour

noun

1. military the time set for the start of an attack or the initial stage of an operation
2. informal.
   a critical time, esp at the commencement of an action

Word History and Origins

Origin of zero hour¹

First recorded in 1915–20

Example Sentences

Weeks later, in early September, the locals were still waiting for “zero hour,” the retaliation they knew was coming.

From The Daily Beast

In a television season that has given us dreck like Zero Hour, Mob Doctor, and Do No Harm, Southland should be a hit.

From The Daily Beast

ABC tries to get back in the ‘Lost’ game with the ridiculous ‘Zero Hour.’

From The Daily Beast

And, yes, there have been and will be far worse shows than Zero Hour that make it onto the air.

From The Daily Beast

I dozed off twice while watching Zero Hour and kept having to rewind to the beginning to this tepid and snooze-inducing pilot.

From The Daily Beast

Around him, he could feel a tenseness creep over his men as the zero hour approached.

From Project Gutenberg

When the zero hour arrives, a soldier must have a clear head, his body must be fit, he must have his nerves under control.

From Project Gutenberg

But Milton's calm voice came across the room to them: "Zero hour," he said, stepping up into the big transmitting chamber.

From Project Gutenberg

The attack, preceded by a brief artillery preparation, was to take place at dawn, the “zero hour” selected.

From Project Gutenberg

Then, sinking down in the snow behind the black bulk of a spruce tree, they awaited the zero hour.

From Project Gutenberg