The Collaborative International Dictionary of English v.0.48:

otherworldly \otherworldly\ adj.
   1. existing outside of or not in accordance with nature.

   Syn: nonnatural, preternatural, transcendental.
        [WordNet 1.5

   2. Not worldly; preparing for or concerned primarily with the
      afterlife; -- of people.
      [WordNet 1.5

WordNet (r) 3.0 (2006):

otherworldly
    adj 1: existing outside of or not in accordance with nature;
           "find transcendental motives for sublunary action"-Aldous
           Huxley [syn: nonnatural, otherworldly,
           preternatural, transcendental]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "otherworldly":
   Christlike, Christly, Elysian, God-fearing, Olympian, airy, alien,
   angelic, arcane, asomatous, astral, autistic, beatific, beatified,
   blessed, bodiless, celestial, daydreaming, daydreamy, decarnate,
   decarnated, dereistic, discarnate, disembodied, eerie, esoteric,
   ethereal, exterrestrial, extramundane, extrasolar, extraterrene,
   extraterrestrial, fey, from on high, ghostly, glorified, godlike,
   godly, godly-minded, good, heavenly, holy, holy-minded,
   hypernormal, hyperphysical, idealistic, immaterial, impalpable,
   imponderable, impractical, in glory, in the clouds, incorporate,
   incorporeal, insubstantial, intangible, mysterious, nonmaterial,
   nonphysical, numinous, occult, paradisaic, paradisal, paradisiac,
   paradisic, phantom, poetic, preterhuman, preternatural,
   preternormal, pretersensual, psychic, pure, pure in heart,
   purehearted, quixotic, righteous, romancing, romantic,
   romanticized, saintlike, saintly, seraphic, shadowy, space,
   spiritual, spiritual-minded, starry-eyed, storybook, superhuman,
   supernal, supernatural, supernormal, superphysical, supersensible,
   supersensual, supramundane, supranatural, transcendental,
   transmundane, unearthly, unembodied, unextended, unfleshly,
   unhuman, unphysical, unpractical, unrealistic, unsubstantial,
   unworldly, visionary, wish-fulfilling