释义 |
zero hour noun 1. a. : the hour at which a previously planned attack or other military operation is started — compare h hour b. : the scheduled time for an action or operation (as the firing of a rocket) to occur or begin — compare countdown 2. : a time when a vital decision or decisive change in the course of events is impending : crisis 3. : the time set as a basis for reckoning the time of day |