Fiction about fiction or fiction in fiction. Usually when a story is presented within a story in more tangible way.
Alternate names: Metastory, Story within story, Fiction within fiction
The first video game about Metafiction was released on September 24, 1993.
This is not about short pieces of fiction found in the world that make them appear more real, but rather when the game/story is about that fiction within fiction. Frame story or any other framing device does not automatically make things metafiction either.