The Collaborative International Dictionary of English v.0.48:

Longitude \Lon"gi*tude\, n. [F., fr. L. longitudo, fr. longus
   long.]
   1. Length; measure or distance along the longest line; --
      distinguished from breadth or thickness; as, the
      longitude of a room; rare now, except in a humorous sense.
      --Sir H. Wotton.
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            The longitude of their cloaks.        --Sir. W.
                                                  Scott.
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            Mine [shadow] spindling into longitude immense.
                                                  --Cowper.
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   2. (Geog.) The arc or portion of the equator intersected
      between the meridian of a given place and the meridian of
      some other place from which longitude is reckoned, as from
      Greenwich, England, or sometimes from the capital of a
      country, as from Washington or Paris. The longitude of a
      place is expressed either in degrees or in time; as, that
      of New York is 74[deg] or 4 h. 56 min. west of Greenwich.
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   3. (Astron.) The distance in degrees, reckoned from the
      vernal equinox, on the ecliptic, to a circle at right
      angles to the ecliptic passing through the heavenly body
      whose longitude is designated; as, the longitude of
      Capella is 79[deg].
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   Geocentric longitude (Astron.), the longitude of a heavenly
      body as seen from the earth.

   Heliocentric longitude, the longitude of a heavenly body,
      as seen from the sun's center.

   Longitude stars, certain stars whose position is known, and
      the data in regard to which are used in observations for
      finding the longitude, as by lunar distances.
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