Meaning

adjective difficult to detect or grasp by the mind or analyze

adjective able to make fine distinctions

adjective working or spreading in a hidden and usually injurious way

originThe adjective is derived from Middle English sotil, soubtil, subtil (“of a person, the mind, etc.: clever, ingenious, penetrating; cunning, sly; insidious; delicate, fine; not dense, light, thin; finely powdered; narrow, slender; etc.”), borrowed from Anglo-Norman sotel, subtil, sutil, Middle French soutil, subtil, sutil, and Old French sotil, soutil, subtil, sutil (“of an object: skilfully…

Etymology from Wiktionary, CC BY-SA 3.0