What does "meta" mean in the context of games? "Meta" means Most Effective Tactics Available. Except it doesn't!
I love the truth and I hate lies. To rewrite history is to falsify it, and the history of our language is the history of our society. The word "meta" traces an important path through gaming culture and I'll be damned if I let it be forgotten.
"Meta" is the shortened form of "metagame", and to understand the concept of metagaming we have to look at imperfect information games like RTSes.
Consider a game where two players choose a card simultaneously at the beginning of the game, and the card chosen influences which player wins. There is a card Foo which wins against almost all other cards. There is also a card Bar which loses against almost all other cards, except it wins against Foo.
When this game is first played, many people will pick Foo as it is superior in almost all situations. However, some players will notice that everyone is picking Foo and start picking Bar. Objectively, Bar is a worse choice looking at the stats within the game, but if you look at what people do outside of the game, Bar is the better choice because it will give you an advantage most of the time in practice. This is the metagame, playing the game not based off the game mechanics, but off of how other players play the game.
The metagame (or meta for short) is constantly shifting and is not directly related to what's objectively good based solely on the game mechanics. Playing the meta involves keeping up with what other players are doing and staying one step ahead. Going back to our hypothetical game, more and more players will start to notice and start picking Bar instead of Foo, until some equilibrium is reached which gives both Foo and Bar players the advantage roughly 50% of the time. However, the players on top of the meta may start to pick Baz, which is strong against Bar. Baz is weak against Foo, but less so than other cards. This gives Baz players an advantage against the ~50% of Bar players and a lower disadvantage against the ~50% of Foo players, netting them a ~60% advantage overall, higher than the 50% of Foo and Bar players. Thus, the meta progresses.
The popularity of these kinds of competitive games has declined greatly in the past decades, and with the speed of information nowadays, any metagame will achieve equilibrium rapidly. Thus, the idea of playing the metagame has fallen out of popularity. "Meta" has been simplified to refer to "what you should do to achieve the best outcome" and is being used in games that lack a metagame, such as single player games.
I am well aware that language changes over time, and I am not salty about the changes. What I am upset about is when people forget the history behind the changes. Humans are short-lived, and their attention spans and memory even more so. I see many gamers nowaday who are ignorant of the history of the word "meta", and the backronym "Most Effective Tactics Available" has created a false etymology.
A false etymology is a lie to future generations, and I hate lies. Though I am but one person, I felt compelled to let you know, dear reader, with the hope that gamers do not forget what the real meta is.