mysterious influence; mysterious effect
Refers to an inexplicable, often subtle or profound influence or effect, sometimes with a spiritual or supernatural nuance. Relatively rare and literary.
この薬草には妙用があると伝えられている。
It is said that this herb has a mysterious effect.
彼の言葉には人を動かす妙用が潜んでいた。
His words held a mysterious influence that moved people.
Compound of 妙 (mysterious, strange) and 用 (use, effect). The exact historical derivation is uncertain, but the term is used in literary and philosophical contexts to denote an inscrutable influence.