- autumnal equinox, September equinox, fall equinox - September 22
--1 is a kind of equinox
--1 is a part of fall, autumn; September, Sep, Sept
Antonyms: vernal equinox, March equinox, spring equinox
- autumnal equinox - (astronomy) the equinoctial point that lies in the constellation of Virgo
--2 is a kind of equinoctial point, equinox