[ 'i:kwɪnɒks , ˌɛkwɪ- ]
■ noun the time or date (twice each year, about 22 September and 20 March) at which the sun crosses the celestial equator, when day and night are of equal length.
↘another term for equinoctial point .
Origin
ME: from OFr. ~e or L. aequinoctium , from aequi- 'equal' + nox , noct- 'night'.