Among academic historians there is a consensus of what a "world war" is - it is a conflict that cannot be solved in terms of existing international diplomatic practices, and requires going "back to the drawing board" and setting up a whole new system of international relations when the dust settles.

So the Thirty Years' War was "world war zero", a classic example of what a world war looks like. It ended with the Westphalian Peace, WWI ended with the League of Nations, WWII ended with the establishment of the UN and its Security Council.

The current clusterfuck will abolish the UN at its end and start something new. The current period will go down in history as a world war.