Nā'dir, n.
n. [Fr., Sp., & It. nadir, from Ar. nadîr, nazîr, opposite, from nazara, to be like, corresponding to, opposite, to look toward.]
Sense 1. That point of the heavens, or lower hemisphere, directly opposite to the zenith; the inferior pole of the horizon; the point directly under the place where we stand.
Sense 2. Hence, the lowest point; the place or 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.