Nadir is a noun that refers to the lowest point.
Having roots in Arabic, our word of the day’s origin is in astronomy. A nadir refers to the point of the celestial sphere that is directly opposite the zenith and vertically downward from the observer. In more common usage, the word simply means ‘a things lowest point.’ For example: I think my athletic career reached its nadir when I struck out five times in a high school baseball game. That was the worst humiliation I’ve ever faced in a sports setting.