Pronunciation: (lon'ji-tOOd", -tyOOd"),[key] —n. 1. Geog.angular distance east or west on the earth's surface, measured by the angle contained between the meridian of a particular place and some prime meridian, as that of Greenwich, England, and expressed either in degrees or by some corresponding difference in time.
2. Astron. a. See celestial longitude. b. See galactic longitude.