n. 1 the part of the celestial sphere directly above an observer (opp. NADIR). 2 the highest point in one's fortunes; a time of great prosperity etc. zenith distance an arc intercepted between a celestial body and its zenith; the complement of a body's altitude.
[ ME f. OF cenit or med.L cenit ult. f. Arab. samt (ar-ra' s) path (over the head) ]