H-hour
[
eych
-ou
uh
r, -ou-er]
/ˈeɪtʃˌaʊər, -ˌaʊ ər/
noun
1.
the time, usually unspecified, set for the beginning of a planned attack.
Origin
H (for
hour
) +
hour
; cf.
D-day
British Dictionary definitions for
H-hour
H-hour
noun
1.
(
military
) the specific hour at which any operation commences
Also called
zero hour