"Designed for, and understood by, the specially initiated alone; not communicated, or not intelligible, to the general body of followers; private; interior. Opposed to exoteric." Source: Webster's Revised Unabridged Dictionary.
"Tremendous is the effort and the vigilance that is needed from second to second, from moment to moment, in order to not fall into illusions. One minute of unawareness is enough for the mind to be already dreaming about something else, distracting it from the job or deed that we are living at the moment."