sub·til·ty /ˈsʌtḷti, ˈsʌbtḷ-/
1. The quality or state of being subtile; thinness; fineness; as, the subtility of air or light.
2. Refinement; extreme acuteness; subtlety.
Intelligible discourses are spoiled by too much subtility in nice divisions. --Locke.
3. Cunning; skill; craft. [Obs.]
To learn a lewd man this subtility. --Chaucer.
4. Slyness in design; artifice; guile; a cunning design or artifice; a trick; subtlety.
O full of all subtility and all mischief. --Acts xiii. 10.
Note: ☞ In senses 2, 3, and 4 the word is more commonly written subtlety.