Source : Webster's Revised Unabridged Dictionary (1913)

Ascension \As*cen"sion\, n. [F. ascension, L. ascensio, fr.
   ascendere. See {Ascend}.]
   1. The act of ascending; a rising; ascent.

   2. Specifically: The visible ascent of our Savior on the
      fortieth day after his resurrection. (--Acts i. 9.) Also,
      Ascension Day.

   3. An ascending or arising, as in distillation; also that
      which arises, as from distillation.

            Vaporous ascensions from the stomach. --Sir T.
                                                  Browne.

   {Ascension Day}, the Thursday but one before Whitsuntide, the
      day on which commemorated our Savior's ascension into
      heaven after his resurrection; -- called also {Holy
      Thursday}.

   {Right ascension} (Astron.), that degree of the equinoctial,
      counted from the beginning of Aries, which rises with a
      star, or other celestial body, in a right sphere; or the
      arc of the equator intercepted between the first point of
      Aries and that point of the equator that comes to the
      meridian with the star; -- expressed either in degrees or
      in time.

   {Oblique ascension} (Astron.), an arc of the equator,
      intercepted between the first point of Aries and that
      point of the equator which rises together with a star, in
      an oblique sphere; or the arc of the equator intercepted
      between the first point of Aries and that point of the
      equator that comes to the horizon with a star. It is
      little used in modern astronomy.

Source : WordNet®

Ascension Day
     n : (Christianity) celebration of the Ascension of Christ into
         heaven; observed on the 40th day after Easter [syn: {Ascension},
          {Ascension of the Lord}]