Metaphysics = the physics of physics
Metascience = studying science itself with science
Metaphilosophy = Philosophy about philosophy itself
Metadata = data describing data
Gaming 'meta' = the game of how to best play the game
'Meta' is one of those ultra-abstract terms that obfuscates the meaning of whatever word it is attached to unless the listener gives or has given the word a fair amount of thought. Ah, then maybe that is why it is being used here.
Metaphysics isn't really the "physics of physics" though. It is part of philosophy, not physics. It isn't even the "philosophy of physics", since that names a branch of philosophy distinct from metaphysics (albeit they do have some points of overlap.) This is an example of where the meaning of a term is different from the sum of its parts.
The philosophical implications of quantum theory (and its interpretations) is one part of the philosophy of physics, but the study of those implications go beyond just metaphysics proper and also extends to other areas of philosophy such as the philosophy of mind, epistemology, the philosophy of logic, etc. Conversely, there are some debates in metaphysics with which contemporary philosophy of physics doesn't concern itself with much, such as the relationship between existence and essence, or the problem of universals.
A "metaverse" is a "universe" in the sense that it's a shared 4D spacetime that you can explore (using some technology to give you a window into it). It's "meta" because it's layered on top of our "base universe": It's there to describe and augment the physical universe we exist in.
For example: If, in your vision (via glasses, or a HUD, or a pane of glass or a brain implant), there's a big 3D arrow hovering above a road then the arrow exists in the "metaverse" and the road exists in the physical universe that the metaverse is describing.
I thought metaverse just meant Second Life 2.0.
Personally, I dislike the term and I believe that it causes people to lose credibility when they use it. However, I can define it to some extent.
Consider the term 'universe' in the context of 'a particular sphere of activity, interest, or experience'. For example, the 'Harry Potter universe'.
The 'metaverse' is simply such a 'universe' that you can't really opt out of, because it's a layer on top of, rather than distinct from, the regular old world. This is why AR is often considered to be such an intrinsic aspect of it.
Now, you might say that 'the internet' is just such a metaverse, but it isn't because it doesn't benefit the people who peddle the buzzword.