n. The moment when the sun crosses the plane of the earth's equator, making the day and night everywhere of equal length (whence the name). There are two annual equinoxes, the vernal, which falls in the spring, namely, on the 21st of March according to the Gregorian calendar, and the autumnal, which falls in the autumn, namely, on the 22d of September. The term equinox is also loosely applied to the equinoctial points (which see, under equinoctial).n. An equinoctial gale or storm; an equinoctial.n. Anything equal; an equal measure.