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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

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

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

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

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

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

In Robert Capa’s photograph of GIs on the USS Samuel Chase just before the D-Day landings, soldiers play craps with French banknotes.

From The Wall Street Journal ● Jul. 15, 2026

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

Around the anniversary of the D-Day invasion on June 6, the whole place turns into a love-fest for America.

From Salon ● Jun. 9, 2026

D-Day was the largest military seaborne operation ever attempted, and marked the start of the campaign to liberate Nazi-occupied north-west Europe.

From BBC ● Jun. 6, 2026

It was like a newspaper on election night; general staff headquarters on D-Day minus one.

From "Cheaper by the Dozen" by Frank B. Gilbreth Jr. and Ernestine Gilbreth Carey