When you create new layers of abstraction between the thing or event, you are becoming more meta.

For example: A footnote that is needed to explain another footnote is meta.

The problem with being meta is that if you add sufficient layers of abstraction or complexity between the original event and the convenient abstractions you create to clarify or explain it, you eventually lose all connection to the original. Generally, you need no more than two or three levels in writing.

Too much meta in your writing leads to meta fog.

In writing, this means your writing sucks.

An acronym, most commonly used in the gaming world, for Most Effective Tactic Available.

When in any form of art; whether it be a story, video game, picture, movie, etc.; the story is explaining itself.

In the gaming world, meta is what the entire community does within one week of the game's release or latest patch, ignoring everything else the game or the game developer has to offer.

In the gaming world. The meta is what is in RIGHT NOW. What are the best strategies, plays, options.. Things of that nature. Often referred to as "Meta-Game".

Meta-HTMLTM is a programming language specifically designed for working within the World Wide Web environment. Although it is a genuine programming language, suitable for large-scale symbolic manipulation, it provides the most commonly wanted Web functionality as built-in primitives, so you don't have to write them.
Check out The White-Paper Manifesto (circa 1996)

a reddit term used to describe posts in a subreddit about or referencing the state of it