subtle

adjective

So slight as to be difficult to detect or describe; elusive.

adjective

Difficult to understand; abstruse.

adjective

Able to make fine distinctions.

adjective

Operating in a hidden, usually injurious way; insidious.

adjective

Characterized by skill or ingenuity; clever.

adjective

Crafty or sly; devious.

Same as subtile, 1.

Same as subtile, 2.