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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

“In the D-day sequence at the end, there are various real-life shots of the soldiers landing on the beaches,” Maras says.

From Los Angeles Times • May 29, 2026

Brendan Fraser and Andrew Scott are fire and ice in this depiction of the run-up to D-day, a secret operation that required total commitment — and no rain.

From Los Angeles Times • May 29, 2026

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

From Los Angeles Times • May 29, 2026

“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

Then, in August 2009, the city decided to pardon the children who had participated in the 1963 D-day and Double D-day protest.

From "While the World Watched: A Birmingham Bombing Survivor Comes of Age during the Civil Rights Movement" by Carolyn Maull McKinstry