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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

See Examples For:

D-day D-Day

“Pressure,” the new World War II movie from director Anthony Maras and writer David Haig, is a hyperfocused look at the days leading up to D-day with a special focus on the weather.

From Los Angeles Times ● May 29, 2026

The success of D-day, a pivotal moment in World War II, partially hinged on the weather forecast.

From Los Angeles Times ● May 29, 2026

After Stagg convinces the leaders to postpone D-day, he is vindicated by a deluge of rain that arrives while everyone is attending church at Southwark House on June 5.

From Los Angeles Times ● May 29, 2026

Stagg was not allowed to make phone calls to her because of the secrecy surrounding D-day.

From Los Angeles Times ● May 29, 2026

The ministers argued among themselves that night—the evening before the march that James Bevel had called D-day.

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

The creation of the unit was announced by French President Emmanuel Macron alongside Zelensky on the 80th anniversary of the D-Day landings in 2024.

From Barron's ● Jul. 13, 2026

Operation Fortitude saw the Allies deploy a faux “First U.S. Army Group” of inflatable tanks and wooden planes to distract from the D-Day invasion.

From The Wall Street Journal ● Jul. 12, 2026

On D-Day, a local orchestra played at Eisenhower’s library in Abilene, Kan.

From The Wall Street Journal ● Jun. 14, 2026

Using the D-Day anniversary to do it is just chef’s kiss, I’d have to say.

From Salon ● Jun. 9, 2026

It even turned out to be crucial for the D-Day invasions.

From "The Woman All Spies Fear" by Amy Butler Greenfield