Source : Webster's Revised Unabridged Dictionary (1913)

Altitude \Al"ti*tude\, n. [L. altitudo, fr. altus high. Cf.
   {Altar}, {Haughty}, {Enhance}.]
   1. Space extended upward; height; the perpendicular elevation
      of an object above its foundation, above the ground, or
      above a given level, or of one object above another; as,
      the altitude of a mountain, or of a bird above the top of
      a tree.

   2. (Astron.) The elevation of a point, or star, or other
      celestial object, above the horizon, measured by the arc
      of a vertical circle intercepted between such point and
      the horizon. It is either true or apparent; true when
      measured from the rational or real horizon, apparent when
      from the sensible or apparent horizon.

   3. (Geom.) The perpendicular distance from the base of a
      figure to the summit, or to the side parallel to the base;
      as, the altitude of a triangle, pyramid, parallelogram,
      frustum, etc.

   4. Height of degree; highest point or degree.

            He is [proud] even to the altitude of his virtue.
                                                  --Shak.

   5. Height of rank or excellence; superiority. --Swift.

   6. pl. Elevation of spirits; heroics; haughty airs. [Colloq.]
      --Richardson.

            The man of law began to get into his altitude. --Sir
                                                  W. Scott.

   {Meridian altitude}, an arc of the meridian intercepted
      between the south point on the horizon and any point on
      the meridian. See {Meridian}, 3.

Source : WordNet®

altitude
     n 1: elevation especially above sea level or above the earth's
          surface; "the altitude gave her a headache" [syn: {height}]
     2: the perpendicular distance from the base of a geometric
        figure to opposite vertex (or side if parallel)
     3: angular distance above the horizon (especially of a
        celestial object) [syn: {elevation}, {EL}, {ALT}]