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• D-day
  D-day

  noun

  the day, usually unspecified, set for the beginning of a planned attack.
• D-Day
  D-Day

  The code name for the first day of a military attack, especially the American and British invasion of German-occupied France during World War II on June 6, 1944 (see invasion of Normandy). This marked the beginning of the victory of the Allies in Europe. Germany surrendered less than a year later.

D-day

American  

[dee-dey] / ˈdiˌdeɪ /

Or D-Day

noun

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

2. June 6, 1944, the day of the invasion of western Europe by Allied forces in World War II.

3. Informal. any day of special significance, as one marking an important event or goal.

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D-day British  

noun

1. 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

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D-Day Cultural  

1. The code name for the first day of a military attack, especially the American and British invasion of German-occupied France during World War II on June 6, 1944 (see invasion of Normandy). This marked the beginning of the victory of the Allies in Europe. Germany surrendered less than a year later.

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Etymology

Origin of D-day

First recorded in 1918; D (for day ) + day; the same pattern as H-hour

Example Sentences

“That was an absolute disaster and yet we remember D-day as one of the great military triumphs in history,” Haig says.

From Los Angeles Times • May 29, 2026

In the film, Scott’s Stagg arrives at Southwark House from Dunstable four days before D-day is planned.

From Los Angeles Times • May 29, 2026

Eisenhower, in particular, felt the magnitude of D-day.

From Los Angeles Times • May 29, 2026

D-day, secretly known as Operation Overlord, was timed based on several factors, including the weather, the tides and the moonlight.

From Los Angeles Times • May 29, 2026

Danny Akee always seemed to have a funny story to tell, even about D-day on Saipan.

From "Code Talker: A Novel About the Navajo Marines of World War Two" by Joseph Bruchac