The Collaborative International Dictionary of English v.0.48:

Occult \Oc*cult"\, v. t.
   To eclipse; to hide from sight.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Occult \Oc*cult"\, a. [L. occultus, p. p. of occulere to cover
   up, hide; ob (see Ob-) + a root prob. akin to E. hell: cf.
   F. occulte.]
   Hidden from the eye or the understanding; invisible; secret;
   concealed; unknown.
   [1913 Webster]

         It is of an occult kind, and is so insensible in its
         advances as to escape observation.       --I. Taylor.
   [1913 Webster]

   Occult line (Geom.), a line drawn as a part of the
      construction of a figure or problem, but not to appear in
      the finished plan.

   Occult qualities, those qualities whose effects only were
      observed, but the nature and relations of whose productive
      agencies were undetermined; -- so called by the schoolmen.


   Occult sciences, those sciences of the Middle Ages which
      related to the supposed action or influence of occult
      qualities, or supernatural powers, as alchemy, magic,
      necromancy, and astrology.
      [1913 Webster]

WordNet (r) 3.0 (2006):

occult
    adj 1: hidden and difficult to see; "an occult fracture";
           "occult blood in the stool"
    2: having an import not apparent to the senses nor obvious to
       the intelligence; beyond ordinary understanding; "mysterious
       symbols"; "the mystical style of Blake"; "occult lore"; "the
       secret learning of the ancients" [syn: mysterious,
       mystic, mystical, occult, secret, orphic]
    n 1: supernatural forces and events and beings collectively;
         "She doesn't believe in the supernatural" [syn:
         supernatural, occult]
    2: supernatural practices and techniques; "he is a student of
       the occult" [syn: occult, occult arts]
    v 1: cause an eclipse of (a celestial body) by intervention;
         "The Sun eclipses the moon today"; "Planets and stars often
         are occulted by other celestial bodies" [syn: eclipse,
         occult]
    2: become concealed or hidden from view or have its light
       extinguished; "The beam of light occults every so often"
    3: hide from view; "The lids were occulting her eyes"

Moby Thesaurus II by Grady Ward, 1.0:

318 Moby Thesaurus words for "occult":
   abstract, abstruse, airy, anagogic, apply to, arcana, arcane,
   arcanum, asomatous, astral, baffling, becloud, beclouded, bedarken,
   bedim, befog, begloom, between the lines, black, black magic,
   black out, blacken, blanket, blind, block, block the light,
   blot out, bodiless, bodilessness, brown, buried, bury, cabala,
   cabalic, cabalism, cabalistic, cabbala, cabbalism, cabbalistic,
   cache, camouflage, canopy, cast a shadow, censored, classified,
   classified information, cloak, close, closed, clothe, cloud,
   cloud over, clouded, conceal, concealed, confidence,
   confidential communication, cope, cover, cover up, covered, covert,
   cowl, dark, darken, darken over, decarnate, decarnated, deep,
   delitescent, dim, dim out, discarnate, disembodied, disguise,
   dissemble, distract attention from, ditch, dormant, eclipse,
   eclipsed, eerie, eeriness, elfdom, encloud, encompass with shadow,
   enigma, enigmatic, ensconce, enshroud, envelop, esoteric,
   esoterica, ethereal, extramundane, extraterrestrial, faerie, fey,
   film, ghostliness, ghostly, gloom, gloss over, guarded secret,
   heavy, hermetic, hermetics, hibernating, hid, hidden, hide, hood,
   hush-hush, hypernormal, hyperphysical, immaterial, immateriality,
   immaterialness, impalpability, impalpable, impenetrable,
   imponderability, imponderable, in a cloud, in a fog, in eclipse,
   in purdah, in the wings, incommunicado, incomprehensible,
   incorporate, incorporeal, incorporeality, incorporeity,
   indecipherable, inexplicable, inextension, inscrutable,
   insubstantial, intangibility, intangible, keep under cover, latent,
   lay on, lay over, lurking, magical, mantle, mask, metaphysic,
   miraculousness, muffle, muffled, murk, mysterious, mysteriousness,
   mystery, mystery of mysteries, mystic, mystical, mystifying,
   nonexteriority, nonmaterial, nonphysical, numinous, numinousness,
   obduce, obfuscate, obfuscated, obnubilate, obscure, obscured,
   obumbrate, occult phenomena, occultate, occultism,
   otherworldliness, otherworldly, overcast, overcloud, overlay,
   overshadow, overspread, perplexing, personal matter, phantom,
   possible, potential, preterhuman, preternatural, preternaturalism,
   preternormal, pretersensual, private, private matter,
   privileged communication, privity, privy, profound,
   profound secret, psychic, psychical research, psychicism, psychics,
   psychism, put on, puzzling, recondite, restricted,
   restricted information, screen, scum, sealed book, secluded,
   secluse, secret, secrete, sequestered, shade, shadow, shadowiness,
   shadowy, shield, shroud, shrouded, sleeping, slur over, smothered,
   somber, sorcery, spirit world, spiritual, spirituality,
   spirituousness, spread over, stash, stifled, submerged, superhuman,
   superhumanity, superimpose, supernatural, supernaturalism,
   supernaturality, supernaturalness, supernature, supernormal,
   supernormalness, superphysical, superphysicalness, superpose,
   supersensible, supersensibleness, supersensual, suppressed,
   supramundane, supranatural, supranaturalism, supranature,
   the occult, the supernatural, the supersensible, the unknown,
   theosophical, theosophist, top secret, transcendental,
   transcendentalism, transmundane, ulterior, unbreatheable,
   under an eclipse, under cover, under house arrest, under security,
   under the surface, under wraps, underground, underlying,
   undisclosable, undisclosed, undivulgable, undivulged,
   unearthliness, unearthly, unembodied, unexplainable, unexplained,
   unextended, unfathomable, unfleshly, unhuman, unknown,
   unmanifested, unphysical, unrevealable, unrevealed, unspoken,
   unsubstantial, unsubstantiality, unsubstantialness, untellable,
   untold, unutterable, unuttered, unwhisperable, unworldliness,
   unworldly, vague, varnish, veil, veiled, virtual, weird, whitewash,
   witchcraft, witchery, wrapped in clouds