He defines it when talking about Magic, where there's the two games. The match "game", once you sit down with your decks and draw 7. And the metagame, where you choose which decks to bring, what sideboard to pick, etc.

If there's a really popular rush deck, do you drop some cards which shut down blue control and put in some anti rush cards? That will help when you match against the rush deck, but if everyone does it, then when you reach the finals you might be against the control deck.

That's the metagame, at least how it's used in those circles.

yes, the author seems to use "metagame" to mean a combination of pre-game strategizing (including creation opponent specific strategy) and post game review (+ absorbing lessons learned into the pre game strategizing for the next game).