The angular distance eastward from the vernal equinox measured along the ecliptic to a great circle drawn through the pole of the ecliptic plane and a celestial body.
(astron.) The arc of the ecliptic measured eastward from the vernal equinox to the point where the ecliptic is intersected by the great circle through the star, planet, etc. and the poles of the ecliptic.
The position of a celestial object east of the vernal equinox along the ecliptic . Celestial longitude is measured in degrees eastward from the vernal equinox (0°) to the point where a great circle drawn through the object and the poles of the ecliptic intersects the ecliptic.