nadir Definition

nadir
noun

1. astron.
The point on the celestial sphere directly beneath the observer and opposite to the zenith.
2. The lowest point of anything, especially the absolute depths, eg of despair or degradation.

Thesaurus: depth, bottom, minimum, zero, rock bottom; Antonym: apex, peak, zenith.

Etymology: 15c: from Arabic nazir-as-samt opposite the zenith.