arcane

from WordNet (r) 3.0 (2006)

arcane
    adj 1: requiring secret or mysterious knowledge; "the arcane
           science of dowsing"

from The Collaborative International Dictionary of English v.0.48

Arcane \Ar*cane"\, a. [L. arcanus.]
   Hidden; secret. [Obs.] "The arcane part of divine wisdom."
   --Berkeley.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

79 Moby Thesaurus words for "arcane":
      abstract, abstruse, cabalistic, censored, classified, close,
      closed, concealed, cryptic, dark, deep, eerie, enigmatic, esoteric,
      extramundane, extraterrestrial, fey, hermetic, hidden, hush-hush,
      hypernormal, hyperphysical, impenetrable, inscrutable, latent,
      mysterious, mystic, mystical, numinous, occult, otherworldly,
      preterhuman, preternatural, preternormal, pretersensual, profound,
      psychic, recondite, restricted, secret, smothered, spiritual,
      stifled, superhuman, supernatural, supernormal, superphysical,
      supersensible, supersensual, suppressed, supramundane,
      supranatural, top secret, transcendental, transmundane, ulterior,
      unaccountable, unbreatheable, uncanny, under security, under wraps,
      undisclosable, undisclosed, undivulgable, undivulged, unearthly,
      unguessed, unhuman, unknowable, unrevealable, unrevealed, unspoken,
      untellable, untold, unutterable, unuttered, unwhisperable,
      unworldly, weird