from The Merriam-Webster Online Dictionary
Main Entry: es·o·ter·ic
Pronunciation: \ˌe-sə-ˈter-ik, -ˈte-rik\
Function: adjective
Etymology: Late Latin esotericus, from Greek esōterikos, from esōterō, comparative of eisō, esō within, from eis into; akin to Greek en in — more at in
Date: circa 1660
1 a : designed for or understood by the specially initiated alone <a body of esoteric legal doctrine — B. N. Cardozo> b : requiring or exhibiting knowledge that is restricted to a small group <esoteric terminology>; broadly : difficult to understand <esoteric subjects>
2 a : limited to a small circle <engaging in esoteric pursuits> b : private, confidential <an esoteric purpose>
3 : of special, rare, or unusual interest <esoteric building materials>
— es·o·ter·i·cal·ly \-i-k(ə-)lē\ adverb
