(noun) From Ancient Greek dramatic tradition, this usually comes after a great revelation (anagnorisis) has occurred, and consists of a reversal of fortunes. Thus, a king who rules wisely for fifty years, then discovers that he killed his father and married his mother without knowing it, is at that point in time a participant in a peripetaeia.
Film Critic 1: "I was relaxing with a few porn vids the other night and it turns out one of them was a gay porn tape that I'd shoplifted by mistake. Well, guess who was starring in that gay tape?"
Film Critic 2: "Dude, I don't know. I don't watch gay porn."
Film Critic 1: "Me neither, but get this: it was Peter North."
Film Critic 2: "No way!"
Film Critic 1: "I swear, it was Peter North. And another guy was doing him up the butt and then he comes all over the schoolroom table."
Film Critic 2: "Well this certainly makes for a very dramatic peripetaeia, coming as it does hot on the heels of an anagnorisis."
Film Critic 1: "Yes, and we might even say that his latent homosexuality is his hamartia."