1. Pertaining to an equinox, or the equinoxes, or to the time of equal day and night; as, the equinoctial line.
2. Pertaining to the regions or climate of the equinoctial line or equator; in or near that line; as, equinoctial heat; an equinoctial sun.
3. Pertaining to the time when the sun enters the equinoctial points; as, an equinoctial gale or storm, that is, one happening at or near the time of the equinox, in any part of the world.
(Science: astronomy) equinoctial colure, the celestial equator; so called because when the sun is on it, the nights and days are of equal length in all parts of the world. See equator. ”Thrice the equinoctial line He circled.
(Science: astronomy)” (Milton) – equinoctial points reckoned in any year from the instant when the mean sun is at the mean vernal equinoctial point.
Origin: L. Aequinoctials, fr. Aequinoctium equinox: cf. F. Equinoxial. See Equinox.