The Collaborative International Dictionary of English v.0.48:

Occultation \Oc`cul*ta"tion\, n. [L. occultatio a hiding, fr.
   occultare, v. intens. of occulere: cf. F. occultation. See
   Occult.]
   1. (Astron.) The hiding of a heavenly body from sight by the
      intervention of some other of the heavenly bodies; --
      applied especially to eclipses of stars and planets by the
      moon, and to the eclipses of satellites of planets by
      their primaries.
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   2. (Fig.:) The state of being occult.
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            The reappearance of such an author after those long
            periods of occultation.               --Jeffrey.
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   Circle of perpetual occultation. See under Circle.
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The Collaborative International Dictionary of English v.0.48:

Eclipse \E*clipse"\ ([-e]*kl[i^]ps"), n. [F. ['e]clipse, L.
   eclipsis, fr. Gr. 'e`kleipsis, prop., a forsaking, failing,
   fr. 'eklei`pein to leave out, forsake; 'ek out + lei`pein to
   leave. See Ex-, and Loan.]
   1. (Astron.) An interception or obscuration of the light of
      the sun, moon, or other luminous body, by the intervention
      of some other body, either between it and the eye, or
      between the luminous body and that illuminated by it. A
      lunar eclipse is caused by the moon passing through the
      earth's shadow; a solar eclipse, by the moon coming
      between the sun and the observer. A satellite is eclipsed
      by entering the shadow of its primary. The obscuration of
      a planet or star by the moon or a planet, though of the
      nature of an eclipse, is called an occultation. The
      eclipse of a small portion of the sun by Mercury or Venus
      is called a transit of the planet.
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   Note: In ancient times, eclipses were, and among
         unenlightened people they still are, superstitiously
         regarded as forerunners of evil fortune, a sentiment of
         which occasional use is made in literature.
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               That fatal and perfidious bark,
               Built in the eclipse, and rigged with curses
               dark.                              --Milton.
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   2. The loss, usually temporary or partial, of light,
      brilliancy, luster, honor, consciousness, etc.;
      obscuration; gloom; darkness.
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            All the posterity of our fist parents suffered a
            perpetual eclipse of spiritual life.  --Sir W.
                                                  Raleigh.
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            As in the soft and sweet eclipse,
            When soul meets soul on lovers' lips. --Shelley.
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   Annular eclipse. (Astron.) See under Annular.

   Cycle of eclipses. See under Cycle.
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WordNet (r) 3.0 (2006):

occultation
    n 1: one celestial body obscures another [syn: eclipse,
         occultation]

Moby Thesaurus II by Grady Ward, 1.0:

85 Moby Thesaurus words for "occultation":
   annular eclipse, blackout, blanketing, blocking, blotting out,
   burial, burying, cementwork, central eclipse, cloaking, clouding,
   coating, concealedness, concealment, coverage, covering,
   covering up, covertness, curtaining, darkening, deception,
   dematerialization, departure, disappearance, disappearing,
   dispersion, dissipation, dissolution, dissolving, eclipse,
   eclipsing, elimination, envelopment, enwrapment, enwrapping,
   erasure, evanescence, evaporation, extinction, fadeaway, fadeout,
   fading, going, hiddenness, hiding, incrustation, interment,
   invisibility, laying on, lunar eclipse, mantling, masking, melting,
   mystification, obduction, obscuration, obscurement, obscuring,
   overlaying, overspreading, pargeting, partial eclipse, passing,
   plasterwork, putting away, screening, secrecy, secretion,
   sheathing, shielding, shrouding, solar eclipse, stuccowork,
   subterfuge, superimposition, superposition, total eclipse,
   uncommunicativeness, upholstering, upholstery, vanishing,
   vanishing point, veiling, wipe, wrapping