/ ˈneɪdɪə(r); NAmE -dɪr/ noun
[ sing. ] ( formal ) the worst moment of a particular situation :
the nadir of his career
Company losses reached their nadir in 1999.
OPP zenith
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WORD ORIGIN
late Middle English (as an astronomical term): via French from Arabic naẓīr (as-samt) opposite (to the zenith).