equinoctial

adj

1. (not-comparable)Of or relating to the spring or autumnal equinox.

   “an equinoctial gale or storm, i.e. one happening at or near the time of the equinox, in any part of the world”

   “In the Assyrian Standard [...] we see the figure of an Archer above that of a galloping Bull, and in another Assyrian Standard, that of Sargon II., we find not only the Archer and the Bull, the two constellations which 4,000 b.c. marked the equinoctial colure, but we may also clearly trace a reference to the two constellations which at the same date marked the solstitial colure, namely, those of the Lion and the Water-man.”

2. (not-comparable)Of or relating to the celestial equator.
3. (not-comparable, uncommon)Equatorial: of or relating to the equator of the Earth.
4. (not-comparable)Of flowers: that open and close at particular times of day.

noun

1. The great circle midway between the celestial poles; the celestial equator.

   “The scorching beams under the equinoctial, or extremity of cold within the circle Arctic, […] cannot avoid or expel this heat, fury, and rage of mortal men.”

2. (rare)The terrestrial equator.

   “Nor is this vveather rare about the Æquinoctiall; by Mariners termed the Tornadoes: and tis ſo vncertaine, that novv you ſhall haue a quiet breath and gale, and ſuddenly an vnexpected violent guſt, and ſtorme, ſo fierce, that many times the ſhips vvill feele no helme.”

3. An equinoctial gale.

   “Heavy with storm the coast-lines grew, / And sharp the equinoctials blew”