The Collaborative International Dictionary of English v.0.48:

Equator \E*qua"tor\, n. [L. aequator one who equalizes: cf. F.
   ['e]quateur equator. See Equate.]
   1. (Geog.) The imaginary great circle on the earth's surface,
      everywhere equally distant from the two poles, and
      dividing the earth's surface into two hemispheres.
      [1913 Webster]

   2. (Astron.) The great circle of the celestial sphere,
      coincident with the plane of the earth's equator; -- so
      called because when the sun is in it, the days and nights
      are of equal length; hence called also the equinoctial,
      and on maps, globes, etc., the equinoctial line.
      [1913 Webster]

   Equator of the sun or Equator of a planet (Astron.), the
      great circle whose plane passes through through the center
      of the body, and is perpendicular to its axis of
      revolution.

   Magnetic equator. See Aclinic.
      [1913 Webster]

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.
      [1913 Webster]

   2. Pertaining to the regions or climate of the equinoctial
      line or equator; in or near that line; as, equinoctial
      heat; an equinoctial sun.
      [1913 Webster]

   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.
      [1913 Webster]

   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.
      [1913 Webster]

            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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

equinoctial line
    n 1: the great circle on the celestial sphere midway between the
         celestial poles [syn: celestial equator, equinoctial
         circle, equinoctial line, equinoctial]