equinox Meaning, Definition & Usage

  1. noun either of two times of the year when the sun crosses the plane of the earth's equator and day and night are of equal length
  2. noun (astronomy) either of the two celestial points at which the celestial equator intersects the ecliptic
    equinoctial point.

WordNet

E"qui*nox noun
Etymology
OE. equinoxium, equenoxium, L. aequinoctium; aequus equal + nox, noctis, night: cf. F. équinoxe. See Equal, and Night.
Definitions
  1. The time when the sun enters one of the equinoctial points, that is, about March 21 and September 22. See Autumnal equinox, Vernal equinox, under Autumnal and Vernal.
    When descends on the Atlantic The gigantic Stormwind of the equinox. Longfellow.
  2. Equinoctial wind or storm. R. Dryden.

Webster 1913