es ‧ o ‧ ter ‧ ic /ˌesəˈterɪk◂, ˌiːsə-/ BrE AmE adjective
[ Date: 1600-1700 ; Language: Greek ; Origin: esoterikos , from esotero 'further inside' , from eiso 'inside' ]
known and understood by only a few people who have special knowledge about something:
the esoteric world of scientific supercomputing
—esoterically /-kli/ adverb