The 2nd zone in the hit 1994 game "Sonic the Hedgehog 3". An aquatic city underwater, resembles more of a temple. Pronounced "Hydro City" not "Hydrossity" because im not a f*cking moron.
According to Patrick Beja from Blizzard Entertainment and The Instance, it is the shock the body feels after the "Polar Bear Challenge", where an individual gets into a hot tub, then jumps into snow, then returns to the hot tub.
Rhys: Why did you masturbate while you jumped out of a window into the pool?: John: Sorry, I have hydroautodefenestratiaphiliaphobiaphilia, I just couldn't help myself. It runs in the family.