esoteric

adjectives

confined to and understandable by only an enlightened inner circle
"a compilation of esoteric philosophical theories"
antonym
is similar to
difficult to penetrate; incomprehensible to one of ordinary understanding or knowledge
"the professor's lectures were so abstruse that students tended to avoid them"; "a deep metaphysical theory"; "some recondite problem in historiography"
is similar to
requiring secret or mysterious knowledge
"the arcane science of dowsing"
is similar to
having a secret or hidden meaning
"cabalistic symbols engraved in stone"; "cryptic writings"; "thoroughly sibylline in most of his pronouncements"- John Gunther
is similar to
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"
see also
confined to particular persons or groups or providing privacy
"a private place"; "private discussions"; "private lessons"; "a private club"; "a private secretary"; "private property"; "the former President is now a private citizen"; "public figures struggle to maintain a private life"