esoteric

adj. private, confidential; meant only for the initiated or the select few

Esotericism refers to the doctrines or practices of esoteric knowledge, or otherwise the quality or state of being described as esoteric, or obscure. Esoteric knowledge is that which is specialized or advanced in nature, available only to a narrow circle of "enlightened", "initiated", or highly educated people. Items pertaining to esotericism may be known as esoterica. Some interpretations of esotericism are very broad and include even unconventional and non-scientific belief systems, typically as contrasted with the "scientific" or "traditional religious" beliefs of the society without or "at large". In contrast, exoteric knowledge is knowledge that is well-known or public; or perceived as informally canonic in society at large.
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Adjective
1. confined to and understandable by only an enlightened inner circle; "a compilation of esoteric philosophical theories"
(antonym) exoteric
(similar) abstruse, deep, recondite
(see-also) private

(a.)
Designed for, and understood by, the specially initiated alone; not communicated, or not intelligible, to the general body of followers; private; interior; acroamatic; -- said of the private and more recondite instructions and doctrines of philosophers. Opposed to exoteric.
  

Esoteric [from Greek esoterikos pertaining to the inner] Applied to the advanced instructions given to qualified candidates in Mysteries or schools of philosophy, first used popularly in Greece by Aristotle. Jesus in the Bible had teachings for his disciples in private, and others for the public, precisely as all other ancient religious and philosophical teachers always had. Esoteric teachings both were and are such as could not be understood or profitably received by those not previously prepared by study and probation. Exoteric or outer teachings were often given in symbolic language which revealed the esoteric meaning only to those who were in possession of the keys to interpretation.