Available Definitions:
1) a. - Thin; not dense or gross; rare; as, subtile air; subtile vapor; a subtile medium.
2) a. - Delicately constituted or constructed; nice; fine; delicate; tenuous; finely woven.
3) a. - Acute; piercing; searching.
4) a. - Characterized by nicety of discrimination; discerning; delicate; refined; subtle.
5) a. - Sly; artful; cunning; crafty; subtle; as, a subtile person; a subtile adversary; a subtile scheme.