For example - let us take a simple number game. Pick a number (in a range) - if you pick one higher than me, you win, if I pick one higher than you, I win - otherwise it's a draw. To make things interesting, we are using modulo math - so 0 is considered to be one greater than n. (or any number greater than n - watch me fudge my definitions)
Now, the metagame. Pick rock paper or scissors. Depending upon what you pick, you get a different range for the main game.
The ultimate metagame would eradicate the 'main' game: Rock allows you to pick '0', paper allows you to pick '1' and scissors allows you to pick '2'. N is 2. Obviously here, winning the metagame ALWAYS causes you to win the main game.
As you expand the range, (rock allows 0-10, paper allows 3-13, scissors allows 6-16, n is 14 - for example) the metagame becomes an interesting factor in the main game - you now have ranges of numbers which you know will cause a draw, but you also have a number which MIGHT win it for you, as well as numbers which SHOULD lose it for you...
Eventually, expand the range far enough, or overlap them completely, and the metagame becomes totally unimportant. Then the main game takes over.
But that's not 'meta', really, is it? It's just adding a new phase to the game, that happens before what is now the second phase. I don't see how it's in any way 'meta' .
Yes - I separated it out clearly to show how it was also a game. Guess I should have addressed that second objection more clearly for classic games. But I think you can see how it works with MtG. Building your decks is a phase which happens out of context of actually playing the game. Separate, happens first. Then, based upon that, you play a second game (the actual game of MtG) the outcome of which is partially (and I would argue on that case, almost solely) determined by the 'Build your deck' game. The 'build your deck' game has no meaning without the 'main' game - and you yourself said that the strategy and so forth of that is intrinsically linked and really 'a part of' the OverGame? that is Magic. So 'Magic' is a big game, which can be split up (for ease of thinking) into a 'DeckBuilding?' and a 'Main' game. I would call the 'DeckBuilding?' game 'meta' because it uses information from the 'Main' game - and influences it. It's a sort of 'game about a game' - hence meta.
Note - I am not putitng any negative connotation on meta here - use any terminology you prefer, I just find this split to be helpful when discussing this sort of issue.
This is, of course, a noddy example - but I hope it gives you some idea of how a MetaGame can be related to, or override, a main game.
In NormalUsage a MetaGame would have, as its elements, the strategies and other 'human elements' surrounding a game.
Examples given on this wiki so far:
The army type your opponent will be using in a wargame. (Regardless of which you choose, you still have a chance - but choosing one that has certain style advantages over your opponents means you may have a better chance)