So slight as to be difficult to detect or describe; elusive, Operating in a hidden, usually injurious way; insidious, Characterized by refinement and niceness in drawing distinctions; nicely discriminating; -- said of persons; ; refined; tenuous; sinuous; insinuating; hence, penetrative or pervasive; -- said of the mind; its faculties, or its operations; ; also, difficult of apprehension; elusive