Meaning of zenith distance

ze'nith dis"tance

Pronunciation: [key]
— Astron. Astron.
  1. the angular distance from the zenith of a point on the celestial sphere to the sphere, measured along a great circle that is perpendicular to the horizon; the complement of the altitude.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.