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 cut off from view by the intervention of another body; hide; conceal; eclipse.
• To undergo occultation; be hidden or concealed, as a star or the intermittent beam of light from a lighthouse.
• 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.

• 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.
• transitive verb To eclipse; to hide from sight.

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