Meaning of celestial longitude

celes'tial lon'gitude

Pronunciation: [key]
— Astron. Astron.
  1. the angular distance of a point on the celestial sphere from the great circle that is perpendicular to the ecliptic at the point of the vernal equinox, measured through 360° eastward parallel to the ecliptic.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.