1. Length; measure or distance along the longest line; distinguished from breadth or thickness; as, the longitude of a room; rare now, except in a humorous sense. The longitude of their cloaks. (Sir. W. Scott) Mine [shadow] spindling into longitude immense. (Cowper)
2. (Science: geography) The arc or portion of the equator intersected between the meridian of a given place and the meridian of some other place from which longitude is reckoned, as from Greenwich, England, or sometimes from the capital of a country, as from Washington or paris. The longitude of a place is expressed either in degrees or in time; as, that of new York is 74 deg or 4 h. 56 min. West of Greenwich.
3. (Science: astronomy) The distance in degrees, reckoned from the vernal equinox, on the ecliptic, to a circle at right angles to the ecliptic passing through the heavenly body whose longitude is designated; as, the longitude of Capella is 79 deg .
(Science: astronomy) Geocentric longitude, the longitude of a heavenly body as seen from the earth. Heliocentric longitude, the longitude of a heavenly body, as seen from the suns center. Longitude stars, certain stars whose position is known, and the data in regard to which are used in observations for finding the longitude, as by lunar distances.