The moment when a character realizes that something awful has happened, or notices that something awful is about to happen, and screams "NOOOOOOOOOOOOOOO!" It can also be used when a character is angrily refusing to do something. Used both seriously and for comic effect. Very common on sitcoms. Sometimes the Big "NO!" ends the episode with a Cliff Hanger. Language matters a lot. For example, Big "NO!" is commonly played straight in Japanese media, due to the equivalent iya's higher screamability. But not very common in Russian, due to the equivalent nyet's very low screamability.