H-hour

[eych-ou^uhr, -ou-er]

noun

Military.

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

H-hour

noun

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

Word History and Origins

Origin of H-hour¹

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