Zenith, a word, like Nadir, borrowed from the Arabic, is the name given to that point of the heavens which is exactly overhead—i.e. in line with the spectator's position and the centre of the earth. It is thus the upper pole of the spectator's horizon, as the nadir is the under pole.
Zenith
Chambers's Encyclopaedia, Volume 10: Swastika to Zyrianovsk and Index, p. 796
Source scan(s): p. 0825