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
source: WordNet 3.0
(astronomy) either of the two celestial points at which the celestial equator intersects the ecliptic
source: WordNet 3.0
The time when the sun enters one of the equinoctial points, that is, about March 21 and September 22. See Autumnal equinox, Vernal equinox, under Autumnal and Vernal.
