Question

What is D-Day?

Answer 1

the day (June 6, 1944) in World War II on which Allied forces invaded northern France by means of beach landings in Normandy.
the day on which an important operation is to begin or a change to take effect.

Answer 2

nice anser

Answer 3

D-Day
noun
noun: D-Day; plural noun: D-Days
the day (June 6, 1944) in World War II on which Allied forces invaded northern France by means of beach landings in Normandy.
the day on which an important operation is to begin or a change to take effect.
"it's D-day at the Websters', as Sally gives Kevin an ultimatum"
Origin

from D for day + day. Compare with H-hour.