Main entry: insidious, pernicious, subtle
Definition: working or spreading in a hidden and usually injurious way
Usage: glaucoma is an insidious disease; a subtle poison
Definition: difficult to detect or grasp by the mind or analyze
Usage: his whole attitude had undergone a subtle change; a subtle difference; that elusive thing the soul
Main entry: subtle
Definition: able to make fine distinctions
Usage: a subtle mind