"I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description [of pornography]; and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that."
- United States Supreme Court Justice Potter Stewart in his decision in Jacobellis v. Ohio.
Merriam-Webster defines trope as a "figure of speech." In storytelling, a trope is just that - a conceptual figure of speech, a storytelling shorthand for some sort of concept that the audience will recognize and understand instantly.
Above all, a trope is a convention. It can be a plot trick, a setup, a narrative structure, a character type, a linguistic idiom... It's like porn; you know it when you see it. When the trope itself becomes intrusive, distracting the viewer rather than serving as shorthand, it has become a cliché. Bad screenwriter. No biscuit!
On this wiki, trope has an even more general meaning of a recognizable pattern - not only within the media works themselves, but also in related aspects such as the behind-the-scenes aspects of creation, the technical features of a medium, and the fan experience. It's even been verbed, as in, "That isn't really different enough from our other tropes to be separately tropeable."
See
Meta Trope Intro for a comparison of the ways that a trope can be used.
