Aequinoctium, ex Adiectiuo æquus & nox. Golum. Cicer.When nightes and daies be of a length: In spring about the eight Talendes of Aprill: In Autumue about the eight Talends of Dctober.Aequinoctiális & hoc equinoctiâle, pen. prod. Quod ad æquinoctium pertinet: vt. Æquinoctialis circulus. Horæ æquinoctiales. Plin. Tempus æquinoctiale. Plin. Cœli furor æquinoctialis. Catull.
Lewis and Short: Latin dictionary
aequĭnoctĭum, i, n. [aequus-nox], the time of equal days and nights, the equinox, Cic. Att. 12, 28, 3; Caes. B. G. 4, 36; cf. id. ib. 5, 23, Varr. L. L. 6, 8 Müll.: autumnale, Liv 31, 47: vernum, id. 33, 3: aestus duobus aequinoctiis maxime tumentes et autumnali amplius quam verno, etc., Plin. 2, 97, 99, 215.