Oh my, an uncoordinated rightist message. Guess that's what happens when the party talking points don't address an issue.

Wikipedia offers a good answer:

A world war is a military conflict affecting the majority of the world's major nations. World wars usually span multiple continents, and are very bloody and destructive.

The term has usually been used to apply to two conflicts of unprecedented scale and slaughter that occurred during the 20th century. They were the First World War, also known as the Great War (1914–1918) and the Second World War (1939–1945).

Some have claimed that the Cold War should be termed a "World War III" and some that the current "War on Terrorism" is "World War IV". However, these characterisations have attracted little support outside the (largely ideological) groups that have used them.