The Collaborative International Dictionary of English v.0.48:

Parallel \Par"al*lel\, n.
   1. A line which, throughout its whole extent, is equidistant
      from another line; a parallel line, a parallel plane, etc.
      [1913 Webster]

            Who made the spider parallels design,
            Sure as De Moivre, without rule or line ? --Pope.
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   2. Direction conformable to that of another line,
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            Lines that from their parallel decline. --Garth.
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   3. Conformity continued through many particulars or in all
      essential points; resemblance; similarity.
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            Twixt earthly females and the moon
            All parallels exactly run.            --Swift.
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   4. A comparison made; elaborate tracing of similarity; as,
      Johnson's parallel between Dryden and Pope.
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   5. Anything equal to, or resembling, another in all essential
      particulars; a counterpart.
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            None but thyself can be thy parallel. --Pope.
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   6. (Geog.) One of the imaginary circles on the surface of the
      earth, parallel to the equator, marking the latitude;
      also, the corresponding line on a globe or map; as, the
      counry was divided into North and South at the 38th
      parallel.
      [1913 Webster +PJC]

   7. (Mil.) One of a series of long trenches constructed before
      a besieged fortress, by the besieging force, as a cover
      for troops supporting the attacking batteries. They are
      roughly parallel to the line of outer defenses of the
      fortress.
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   8. (Print.) A character consisting of two parallel vertical
      lines (thus, ) used in the text to direct attention to a
      similarly marked note in the margin or at the foot of a
      page.
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   9. (Elec.) That arrangement of an electrical system in which
      all positive poles, electrodes, terminals, etc., are
      joined to one conductor, and all negative poles, etc., to
      another conductor; -- called also multiple. Opposed to
      series.

   Note: Parts of a system so arranged are said to be

   in parallel or

   in multiple.
      [Webster 1913 Suppl.]

   Limiting parallels. See under Limit, v. t.

   Parallel of altitude (Astron.), one of the small circles of
      the sphere, parallel to the horizon; an almucantar.

   Parallel of declination (Astron.), one of the small circles
      of the sphere, parallel to the equator.

   Parallel of latitude.
      (a) (Geog.) See def. 6. above.
      (b) (Astron.) One of the small circles of the sphere,
          parallel to the ecliptic.
          [1913 Webster]

WordNet (r) 3.0 (2006):

parallel of latitude
    n 1: an imaginary line around the Earth parallel to the equator
         [syn: latitude, line of latitude, parallel of
         latitude, parallel]