Source : Webster's Revised Unabridged Dictionary (1913)

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.

   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.

   {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}.

            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.

Source : WordNet®

equinoctial line
     n : the great circle on the celestial sphere midway between the
         celestial poles [syn: {celestial equator}, {equinoctial
         circle}, {equinoctial}]