Webster's Revised Unabridged Dictionary · 1913

Equinoctial

Equinoctial , adjective

[Latin aequinoctials, from aequinoctium equinox: compare French équinoxial. See Equinox.]

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.
Thrice the equinoctial line He circled. — Milton

Equinoctial , noun

The equinoctial line.