occult

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Of, relating to, or dealing with supernatural or magical influences, agencies, or occurrences.
• adjective Available only to the initiate; secret or mysterious: synonym: mysterious.
• adjective Beyond the realm of human comprehension; inscrutable.
• adjective Hidden from view; concealed.
• adjective Medicine Detectable only by microscopic examination or chemical analysis, as a minute blood sample.
• adjective Not accompanied by readily detectable signs or symptoms.
• noun Occult practices or techniques.
• intransitive verb To conceal or cause to disappear from view.
• intransitive verb Astronomy To conceal by occultation.
• intransitive verb To become concealed or extinguished at regular intervals.

from The Century Dictionary.

• To undergo occultation; be hidden or concealed, as a star or the intermittent beam of light from a lighthouse.
• To cut off from view by the intervention of another body; hide; conceal; eclipse.
• Not apparent upon mere inspection, nor deducible from what is so apparent, but discoverable only by experimentation; relating to what is thus undiscoverable by mere inspection: opposed to manifest.
• Mysterious; transcendental; beyond the bounds of natural knowledge.
• Synonyms Latent, Covert, etc. (see secret), unrevealed, recondite, abstruse, veiled, shrouded, mystic, cabalistic.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To eclipse; to hide from sight.
• adjective Hidden from the eye or the understanding; invisible; secret; concealed; unknown.
• adjective (Geom.) a line drawn as a part of the construction of a figure or problem, but not to appear in the finished plan.
• adjective those qualities whose effects only were observed, but the nature and relations of whose productive agencies were undetermined; -- so called by the schoolmen.
• adjective 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb transitive, astronomy To cover or hide from view.
• verb transitive, rare To dissimulate, conceal, or obfuscate.
• adjective medicine Secret; hidden from general knowledge; undetected
• adjective Related to the occult; pertaining to mysticism, magic, or astrology.
• adjective Esoteric.
• noun Supernatural affairs.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun supernatural forces and events and beings collectively
• verb cause an eclipse of (a celestial body) by intervention
• adjective hidden and difficult to see
• noun supernatural practices and techniques
• verb hide from view
• adjective having an import not apparent to the senses nor obvious to the intelligence; beyond ordinary understanding
• verb become concealed or hidden from view or have its light extinguished