1. [ noun ] either of two times of the year when the sun crosses the plane of the earth's equator and day and night are of equal length
Related terms: cosmic_time autumnal_equinox vernal_equinox
2. [ noun ] (astronomy) either of the two celestial points at which the celestial equator intersects the ecliptic
Synonyms: equinoctial_point
Related terms: celestial_point autumnal_equinox vernal_equinox astronomy