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 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¡ or 4 h. 56 min. west of greenwich.-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¡.