autumnal equinox

autumnal equinox

n.

1. The point at which the ecliptic intersects the celestial equator, the sun having a southerly motion.

2. The moment at which the sun passes through the autumnal equinox, about September 23, marking the beginning of autumn in the Northern Hemisphere.

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autumnal equinox  (ô-tmnl)

See under equinox.

Thesaurus

Noun	1.	autumnal equinox - September 22                         fall equinox, September equinox Sep, Sept, September - the month following August and preceding October equinox - 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 autumn, fall - the season when the leaves fall from the trees; "in the fall of 1973" March equinox, spring equinox, vernal equinox - March 21
	2.	autumnal equinox - (astronomy) the equinoctial point that lies in the constellation of Virgo astronomy, uranology - the branch of physics that studies celestial bodies and the universe as a whole equinoctial point, equinox - (astronomy) either of the two celestial points at which the celestial equator intersects the ecliptic