esoteric

An esoteric doctrine or treatise; esoteric philosophy.

One who believes, or is an initiate, in esoteric doctrines or rites.

Intended for or likely to be understood by only a small number of people with a specialized knowledge or interest, or an enlightened inner circle.

“The writing in this manual is very esoteric; I’d need a degree in engineering just to understand it!”

Having to do with concepts that are highly theoretical and without obvious practical application; often with mystical or religious connotations.

Confidential; private.

“an esoteric meeting”