1. A synonym for a plot twist or turn in a story (eg, book, movie) that is extremely convoluted and anti-climactic that makes something that originally had good potential seem completely pointless.
2. The film of the same name by M. Night Shymalan (he used to make kickass movies like Signs and the Sixth Sense) that birthed this definition. It starts with people mysteriously killing themselves like under a trance, but the twist is that plants are giving off toxens that are causing humans to do it. An unintentional comedy.
1. Eric's fanfic was really good, and had a lot of potential, but in the end he pulled a 'The Happening' and gave it a shitty anti-climactic twist that insulted the reader's intelligence and amde them feel like they'd just wasted a lot of time.