Nadir

Part of speech: noun (n.)

1. That point of the heavens, or lower hemisphere, directly opposite the zenith; the inferior pole of the horizon; the point of the celestial sphere directly under the place where we stand.

2. The lowest point; the time of greatest depression. The seventh century is the nadir of the human mind in Europe. Hallam. Nadir of the sun (Astron.), the axis of the conical shadow projected by the earth. Crabb.