nadir
/ˈneɪdɪə(r)/noun
in sing.
1- the lowest point in the fortunes of a person or organization最低点; 最不幸的时刻：
the 1420s marked the nadir of French fortunes.
15世纪20年代是法国最不幸的时期。
1.1
- Astronomy the point on the celestial sphere directly below an observer【天文】天底。ZENITH的反义词。
词源
late Middle English (in the astronomical sense)： via French from Arabic naẓīr （as-samt） 'opposite (to the zenith)'.