Either of the two times during a year when the sun crosses the celestial equator and when the length of day and night are approximately equal;the vernal equinox or the autumnal equinox.是什么意思_Either of the two times during a year when the sun crosses the celestial equator and when the length of day and night are approximately equal;the vernal equinox or the autumnal equinox.在线翻译_英语_读音_用法_例句