nadir, n. [F., Sp., & It. nadir; all fr. Ar. nazīru's samt nadir, prop., the point opposite the zenith (as samt), in which nazīr 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. [1913 Webster]
The lowest point; the time of greatest depression. [1913 Webster]
"The seventh century is the nadir of the human mind in Europe." [1913 Webster]

Nadir of the sun (Astron.), the axis of the conical shadow projected by the earth. Crabb.

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OXFORD DICTIONARY

nadir, n.
1 the part of the celestial sphere directly below an observer (opp. ZENITH).
2 the lowest point in one's fortunes; a time of deep despair.

Etymology

ME f. OF f. Arab. nazir (as-samt) opposite (to the zenith)

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THESAURUS

nadir

base, baseboard, basement, bedrock, bottom, chassis, dado, foot, footing, foundation, frame, keel, lower strata, lowest level, lowest point, mopboard, shoemold, sole, toe, underlying level, wainscot

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ROGET THESAURUS

nadir

Base

N base, basement, plinth, dado, wainscot, baseboard, mopboard, bedrock, hardpan, foundation, substructure, substratum, ground, earth, pavement, floor, paving, flag, carped, ground floor, deck, footing, ground work, basis, hold, bilge, bottom, nadir, foot, sole, toe, hoof, keel, root, centerboard, bottom, undermost, nethermost, fundamental, founded on, based on, grounded on, built on.

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