Meta (from the Greek preposition and prefix meaning "beyond") is a prefix used in English to indicate a concept which is an abstraction behind another concept, used to complete or add to the latter.
The game = ALL rules, all maps, all figures.
The meta game = Only the rules, maps, tactics and figures in combinations that players actually use.
"META = most effective tactics available" is a sarcastic backronym, that I actually did not intend to use here.
Edited by DerBaer