autumnal equinox

== English == === Pronunciation === === Noun === autumnal equinox (plural autumnal equinoxes) (astronomy) The moment when the sun appears to cross the celestial equator while tilting away from the observer, taking place in September in the northern hemisphere and March in the southern hemisphere. ==== Synonyms ==== fall equinox ==== Coordinate terms ==== summer solstice vernal equinox winter solstice ==== Translations ====