expression, noun-modifying (irregular)
inscrutable; unfathomable; unpredictable
Literary, formal phrase meaning something is beyond comprehension or impossible to measure or predict. Often used to describe profound or mysterious things. The phrase is a fixed expression derived from classical Chinese.
See also: 端倪
彼の才能は端倪すべからざるものがある。
His talent is truly unfathomable.
The power of nature is inscrutable.