Zenith

zen′ith, n. 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): greatest height, summit of ambition, .— adj. Zen′ithal .— ns. Zen′ith-dis′tance , the angular distance of a heavenly body from the zenith; Zen′ith-sec′tor , an instrument for measuring zenith-distances. [Fr., through Sp. zen it , from Ar. samt , short for samt-ur-ras , lit. 'way of the head.']