The Collaborative International Dictionary of English v.0.48:

Horoscope \Hor"o*scope\, n. [F. horoscope, L. horoscopus, fr.
   Gr. ?, adj., observing hours or times, esp. observing the
   hour of birth, n., a horoscope; ? hour + ? to view, observe.
   See Hour, and -scope.]
   1. (Astrol.)
      (a) The representation made of the aspect of the heavens
          at the moment of a person's birth, by which the
          astrologer professed to foretell the events of the
          person's life; especially, the sign of the zodiac
          rising above the horizon at such a moment.
      (b) The diagram or scheme of twelve houses or signs of the
          zodiac, into which the whole circuit of the heavens
          was divided for the purposes of such prediction of
          fortune.
          [1913 Webster]

   2. The planisphere invented by Jean Paduanus.
      [1913 Webster]

   3. A table showing the length of the days and nights at all
      places. --Heyse. Horoscoper

WordNet (r) 3.0 (2006):

horoscope
    n 1: a prediction of someone's future based on the relative
         positions of the planets
    2: a diagram of the positions of the planets and signs of the
       zodiac at a particular time and place

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "horoscope":
   aspect, astrodiagnosis, astrology, astromancy,
   genethliac astrology, genethliacism, genethliacs, genethlialogy,
   horoscopy, house, mansion, mundane astrology, mundane house,
   nativity, natural astrology, planetary house, stargazing, zodiac