esoteric
e-so-ter-ic
adjective
Understood by only a small number of people with specialised knowledge or interest.
"His lecture on ancient philosophy was too esoteric for most."
Thesaurus
Synonyms: orphic, deep, mystic, occult, recondite, secret, cabalistic, mysterious, mystical, arcane, qabalistic, abstruse
Antonyms: exoteric