The Collaborative International Dictionary of English v.0.48:

Equinoctial \E`qui*noc"tial\, a. [L. aequinoctials, fr.
   aequinoctium equinox: cf. F. ['e]quinoxial. See Equinox.]
   1. Pertaining to an equinox, or the equinoxes, or to the time
      of equal day and night; as, the equinoctial line.
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   2. Pertaining to the regions or climate of the equinoctial
      line or equator; in or near that line; as, equinoctial
      heat; an equinoctial sun.
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   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.
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   Equinoctial colure (Astron.), the meridian passing through
      the equinoctial points.

   Equinoctial line (Astron.), 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.
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            Thrice the equinoctial line
            He circled.                           --Milton.

   Equinoctial points (Astron.), the two points where the
      celestial and ecliptic intersect each other; the one being
      in the first point of Aries, the other in the first point
      of Libra.

   Equinoctial time (Astron.) reckoned in any year from the
      instant when the mean sun is at the mean vernal
      equinoctial point.
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