It derives from the italian word "discesa" (fall)- Discesa-discesazza-scesazza, and it's used among youngsters from Genoa to indicate the rude,sudden and unexpected ending of a light-hearted or exciting moment. It's the rapid fading away of excitement and joy cause of an undesired, sad event.
1. At the end of an holiday in Spain with your best friends, it comes to your mind that on monday at 8 o'clock you'll have to be at work and ,realising it so suddenly, you feel incredibly sad and you say: Che Scesazza! ("che" in this case is the italian for "what a..")
2. At a party, having fun, dancing and drinking. All of a sudden music stops at only 3 o'clock am. And realising that everybody feel bothered and rudely woken up from a dream, you describe thi general feeling by saying: "la scesazza".