4th wall

Noun

fourth wall (plural fourth walls)

1. (idiomatic, performing arts) The imaginary invisible wall at the front of the stage in a proscenium theatre, through which the audience sees the action in the world of the play.
   • This is a flat, unnecessary, and strangely disturbing denial of the fourth-wall convention, that unwritten agreement between playwright and playgoer whereby you think of yourself at the theatre as a privileged, exonerated, comfortably seated eavesdropper.1916 February 20, “Second Thoughts on First Nights”, in New York Times, page X7
2. (broadly) The boundary between the fiction and the audience.
   • Even though you, the author, may be maintaining a fourth wall between your characters and your readers, he, the narrator, is not keeping that fourth wall between himself and the audience he thinks he's telling the story to.1999, Orson Scott Card, (Please provide the book title or journal name)