Simple Definition:

Meta means referring to itself or being self-referential. It is used to describe something that is about itself or is aware of its own characteristics or qualities. For example, in a conversation about a TV show where characters discuss the show’s plot or make references to being in a TV show, that would be considered meta.

Very Simple Definition:

Meta means talking about or referencing itself. For example, when characters in a TV show talk about being in a TV show, that’s meta.