秘ひ説せつ

noun

secret theory; esoteric doctrine

Refers to a theory or teaching that is kept hidden or known only to a select group. Often used in religious, philosophical, or occult contexts.

• その宗しゅう派はには、外がい部ぶには明あかされない秘ひ説せつが伝つたわっている。

  That sect has a secret doctrine that is not revealed to outsiders.