a date on which something important is expected to happen 重大事情预定发生日;计划行动开始日 CultureThe Allies were led by General Dwight D Eisenhower, and defeated the German forces defending the beaches. The secret name of the operation was 'Overlord'. It is also often called the Normandy landings. The 'D' is short for 'day'. In the First World War 'H-hour' was used for the time of a planned attack.see also the Mulberry harboursWord OriginFrom the name given to 6 June 1944, the day on which the British, US and other armies landed on the beaches of northern France in the Second World War.