I've noticed that a few creatures have the "titan" tag (here's a D&D Beyond search) but I'm not sure what that tag means.
I noticed the other day in my Monster Manual when looking at the Empyrean and wondered if it had anything to do with titans of Greek mythology (since that's what the Empyrean makes me think of) – but then the Tarrasque is also listed as a titan, so there goes that theory.
I wondered also if it's to do with their size, since the Tarrasque is extra big, even for a Gargantuan-sized creature, but then the the Empyrean and a few others are only Huge, not Gargantuan, so that doesn't make sense either.
I have not seen this tag defined in the Monster Manual, only a small section on "tags" (link to basic rules, listed below all the creature types) that basically says that tags don't mean anything. But even if there are no "rules" about titans, the term must still mean something, like how the "demon" or "shapeshifter" tags still mean something in-universe, at least.
Have I missed something? Although I accept that there are no "rules" about titans, there must still be mention of it somewhere as to how a "titan" creature is different from a non-titan creature. Is there any other official description of what this tag means?
What does the "titan" monster tag mean?