H-hour

[ eych-ouuhr, -ou-er ]

noun

, Military.

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

H-hour

noun

1. military the specific hour at which any operation commences Also calledzero hour

Word History and Origins

Origin of H-hour¹

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

Example Sentences

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

From Project Gutenberg