Esoteric often describes knowledge that requires specific training or education to understand. His esoteric expertise in medieval literature won him the teaching position.
Pro Tip 2/3
Narrow Audience
If something is esoteric, it's not designed for the broad public but for a particular group of enthusiasts. The seminar catered to an esoteric audience of ancient language scholars.
Pro Tip 3/3
Not Mainstream
Use it for ideas or works that are not commonly known or popular in mainstream culture. She enjoys music from esoteric genres that rarely play on the radio.