Na"dir (?), n. [F., Sp., & It. nadir; all fr. Ar. nasiru's samt nadir, prop., the point opposite the zenith (as samt), in which nasir means alike, corresponding to. Cf. Azimuth, Zenith.]
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.
The lowest point; the time of greatest depression.
The seventh century is the nadir of the human mind in Europe.
Nadir of the sun Astron., the axis of the conical shadow projected by the earth.
© Webster 1913.