D-day(redirected from D Day)
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1. The unnamed day on which an operation or offensive is to be launched.
2. The day on which the Allied forces invaded France during World War II (June 6, 1944).
1. (Historical Terms) the day, June 6, 1944, on which the Allied invasion of Europe began
2. the day on which any large-scale operation is planned to start
[C20: from D(ay)-day; compare H-hour]
1. a day set for beginning something.
2. June 6, 1944, the day of the invasion of W Europe by Allied forces in World War II.
[1915–20; Dutch (for day) + day]