Esoteric

/ˌes.əˈter.ɪk/ adjective medium

Understood by or intended for only a small group with specialized knowledge.

The seminar covered such esoteric aspects of tax law that even some lawyers in the audience looked lost.

Memory Trick

The word comes from a Greek term meaning 'further within' — esoteric knowledge is kept further inside a small circle, out of reach of outsiders.