Emily Dickinson Lexicon

SUB'TIL-TY, n. [Fr. subtilité; L. subtilitas.]

1. Thinness; fineness; exility; in a physical sense; as, the subtilty of air or light; the subtilty of sounds. – Bacon. Grew.
2. Refinement; extreme acuteness. Intelligible discourses are spoiled by too much subtilty in nice divisions. – Locke.
3. Slyness in design; cunning; artifice; usually but less properly written subtlety.