1.  autumnal equinox(n = noun.time) fall equinox, september equinox - September 22;
is a kind of equinox
is a part of sep, sept, september, autumn, fall
Antonym: vernal equinox

2.  autumnal equinox(n = noun.location) - (astronomy) the equinoctial point that lies in the constellation of Virgo;
is a kind of equinoctial point, equinox

N  evening, eve, decline of day, fall of day, close of day, candlelight, candlelighting, eventide, nightfall, curfew, dusk, twilight, eleventh hour, sunset, sundown, going down of the sun, cock-shut, dewy eve, gloaming, bedtime, afternoon, postmeridian, p, m, autumn, fall, fall of the leaf, autumnal equinox, Indian summer, St. Luke's summer, St. Martin's summer, midnight, dead of night, witching hour, witching hour of night, witching time of night, winter, killing time, vespertine, autumnal, nocturnal, midnight, the outpost of advancing day, sable-vested Night, this gorgeous arch with golden worlds inlay'd.

autumnal, equinox, fall equinox, march equinox, september equinox, spring equinox, vernal equinox