- Pertaining to an equinox, or the equinoxes, or to the
time of equal day and night; as, the equinoctial line. - Pertaining to the regions or climate of the
equinoctial line or equator; in or near that line; as, equinoctial
heat; an equinoctial sun. - 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.