These are the kinds of questions that are real head-scratchers I think for historians reading the subreddit, because it is not always clear what the questioner has in mind. They seem to be thinking of something specific, but it reads like a guessing game: "bet you can't guess what I'm thinking!"

So, assuming the OP does not mean, "Was there a secret world war whose history has been completely suppressed?" but instead, "Aren't there past wars that deserve to be called 'world wars', the answer that is, "Sort of, maybe, from a certain point of view."

It's not as if "world war" is a concept that has a specific, well-understood technical definition. World War I only became "I" after there was a "II": before 1939 it felt as if it were an unprecedented event in the lives of those who fought it, a war that involved a scale that was completely new to the human species. Battles in World War I were fought across all of Western and Eastern Europe, in the Middle East, in Africa, in Asia and in the Pacific. If that is the scale that defines a "world war", then one had never happened before.

Are there other conflicts that you could think of as being "world wars"? Yes, in a couple of senses. Part of the problem here that we are still very conditioned to think of war as a formal, declared conflict between nation-states that have firm control of a highly defined and bounded territory and who can mobilize their entire societies to engage in this conflict, when in fact that is a pretty unusual way to think of violent conflict between rivalrous groups and political units in the wider span of human history--far more conflicts are informal, undeclared, involve small groups within a given society, are at least somewhat ritualized or ceremonial, do not involve potential conquest or territorial acquisition, and have no simple date where they begin or end in a definitive way.

So for example, the Cold War was certainly global. By the classic modern definition it was not a single "war" formally declared between two clear groups of nation-state adversaries, so few would call it "World War III". There have been classic modern definitions of war involving many nation-states (as opposed to just two adversaries) that you might call "world wars"--the Korean War is one and another would be the Eastern Congo War that involved multiple African nations formally and a few other informal combatants.

You could also make a plausible argument that wars that involved most of the known powers of a fairly bounded historical region--that was essentially the "known world" for most of the combatants--were "world wars". That Alexander's conquests did not involve the Americas or East Asia when neither of those were particularly known to him nor most of the combatants might mean that his conquests were a world war. The conquests of the Mongol Empire under Genghis Khan and his immediate successors might qualify as a "world war"--at least as "wars that were (semi) global in scope)."

But I'm not sure there's much to be gained by trying to relabel World War I and II as part of a much wider lineage of semi-global, almost-global, very-widespread, big-scale wars. There are good reasons to see them as unlike anything else in human experience--and to hope in so doing that World War II is the last of their kind.