World War 2
Definition
A global military conflict that lasted from 1939 to 1945, involving the vast majority of the world's countries and organized into two opposing military alliances: the Allies and the Axis.
The most widespread and deadliest conflict in human history, characterized by the use of mass strategic bombardment, the Nazi Holocaust, and the initial development and use of nuclear weapons.
Examples
My grandfather could tell stories about World War 2 all night, mostly focusing on how difficult it was to find decent coffee in the trenches.
If World War 2 had been fought on social media, the comment sections would have made the actual nuclear fallout look like a minor inconvenience.
Trying to explain the complex alliances of World War 2 to someone who thinks history started in 2010 is a task reserved only for the most patient of educators.