META. Greek prefix or abbreviation?

So! me and a friend of mine got into a discussion of the meaning of the word/abbreviation "META"

From his perspective it's an abbreviation that stands for Most Effective Tactic Available. Whereas I said it's short for Meta-game, meaning the "game within a game." -=INCEPTION BWAAAAAAAAH=- So we decided to leave it up to the lovely people of the community to tell us.

(I know this is a question of semantics, since both terms mean essentially the same, but still we need some comfort and closure for our discussion)