fall equinox

Thesaurus

Noun

1.

fall equinox - September 22 autumnal equinox, September equinoxSep, Sept, September - the month following August and preceding Octoberequinox - 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 lengthautumn, fall - the season when the leaves fall from the trees; "in the fall of 1973"