TL;DR: "beyond".
NTL;R (not too long, reading):
First you have an Ancient Greek word, ⟨μετά⟩ metá "between, along with, besides, following, afterwards". It's a messy word, given it works as a preposition and adverb and even prefix, and depending on the case of the following word you can tweak the meaning further.
Then you have Aristotle writing two collections of works, that were eventually called:
- ⟨Τὰ Φυσικά⟩ Tà Physiká "The Nature", or "The Natural World". Also called "Physics".
- ⟨Μετὰ τὰ Φυσικά⟩ Metà tà Physiká "After The Nature", or "After the Natural World". Also called "Metaphysics".
Whoever called the second book this way (not Aristotle himself, I think?) meant the book was supposed to be read after the first one, because it's considerably more abstract than the first one. And it leans more into what we call today Philosophy, while the first one would be more of what we'd call Science.
Time goes by. People started interpreting "Metaphysics" as if it meant "Beyond Physics", or "The Nature beyond Nature", due to its content. And then they picked that prefix, and plopped it in other words to imply recursion, like:
- metagame - the game beyond the game. For example, you pick PvP battles on a game and build a competition out of it.
- metadata - the data beyond the data. For example, when and where a file was created.
- metatheatre - aspects of a theatrical play that highlight it's a play (break its fourth wall).
- metalanguage - language being used to explain language. Like this whole comment.
- etc.
"The meta" is usually "the metagame".