The nadir is the lowest point in somebody's fortunes. Reach its nadir, the nadir of his career, at the very nadir.
It is the opposite of zenith, and both came into English from Arabic astronomy: the nadir is the point directly beneath you, opposite the zenith overhead. The figurative use is now far commoner than the astronomical one.
1nounnadirThe lowest point in somebody's fortunes.
“Losing his job and his house in the same month was the nadir of his life.”
nadir is a low point.
The Arabic behind it names the point opposite the top of the sky. The nadir is the bottom, as far down as it goes.
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Arabic nazir as-samt means opposite the zenith, and reached English through medieval Latin.
Arabic
نَظِير السَّمْت
Medieval Latin
nadir
English, today
nadir
Built from
From Medieval Latin nadir, from Arabic نَظِير السَّمْت, composed of نَظِير (“counterpart, corresponding to”) and سمت (“the zenith”).
Etymology from Wiktionary, CC BY-SA