Of fiction, especially theater, film, or television, to break the illusion of separation between the audience and the fiction itself, either intentionally or unintentionally. Taken originally from theater, in which the fourth wall describes the invisible "wall" that stands between the audience and the stage. We were enjoying the play, but one of the actors kept breaking the fourth wall by glaring at the audience any time someone made any noise. I love shows that break the fourth wall—it makes me feel like I'm in on the joke.