The term 'self-referential, informally' can be summarized as 'meta, ' which is a four-letter word. Meta is an adjective that is used to describe something that refers to itself or is self-referential. It is often used in the context of literature, film, and other forms of media, where it is used to describe works that are self-referential or comment on themselves. It is also used in philosophy and psychology to refer to ideas or concepts that refer to themselves.