esoteric

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es·o·ter·ic /ˌɛsəˈtɛrɪk/ Pronunciation Key - Show Spelled Pronunciation[es-uh-ter-ik] Pronunciation Key - Show IPA Pronunciation
–adjective 1. understood by or meant for only the select few who have special knowledge or interest; recondite: poetry full of esoteric allusions.
2. belonging to the select few.
3. private; secret; confidential.
4. (of a philosophical doctrine or the like) intended to be revealed only to the initiates of a group: the esoteric doctrines of Pythagoras.
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[Origin: 1645–55; < Gk esōterikós inner, equiv. to ester(os) inner + -ikos -ic]

—Related forms
es·o·ter·i·cal·ly, adverb
—Synonyms 1. abstruse, arcane, cryptic, enigmatic.
Dictionary.com Unabridged (v 1.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.