equinox
equi.nox \'e--kw*-.na:ks, 'ek-w*-\ n [ME, fr. MF or ML; MF equinoxe, fr. ML equinoxium, alter. of L a]equinoctium, fr. aequi- equi- + noct-, nox night - more at NIGHT 1: either of the two times each year when the sun crosses the equator and d ay and night are everywhere of equal length, being about March 21 and September 23 2: either of the two points on the celestial sphere where the celestial equ ator intersects the ecliptic