H-hour

American  

[eych-ou^uhr, -ou-er] / ˈeɪtʃˌaʊər, -ˌaʊ ər /

noun

Military.

1. the time, usually unspecified, set for the beginning of a planned attack.

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H-hour British  

noun

1. Also called: zero hour.  military the specific hour at which any operation commences

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Etymology

Origin of H-hour

First recorded in 1918; H (for hour ) + hour; cf. D-day

Example Sentences

See Examples For:

H-hour

Stormed Utah Beach at H-hour on D-Day as part of the 4th Infantry Division.

From Washington Post

So complete was Big Three solidarity that a General Motors public relations man was overheard phoning his Chrysler counterpart to tell him that H-hour for the release of the statements had come.

From Time Magazine Archive

Only 15 minutes before H-hour, the picture grew shaky, wobbled, then disappeared.

From Time Magazine Archive

Getting from one side to the other meant a H-hour ferry ride or a roundabout inland route of some 100 miles.

From Time Magazine Archive

We breathed the standard helium-oxygen mix at normal pressure until about four hours before H-hour.

From The Trouble with Telstar by Schoenherr, John