The Collaborative International Dictionary of English v.0.48:
Subtle \Sub"tle\, a. [Compar. Subtler; superl. Subtlest.]
[OE. sotil, subtil, OF. soutil, later subtil, F. subtil, L.
subtilis; probably, originally, woven fine, and fr. sub under
+ tela a web, fr. texere to weave. See Text, and cf.
1. Sly in design; artful; cunning; insinuating; subtile; --
applied to persons; as, a subtle foe. "A subtle traitor."
2. Cunningly devised; crafty; treacherous; as, a subtle
3. Characterized by refinement and niceness in drawing
distinctions; nicely discriminating; -- said of persons;
as, a subtle logician; refined; tenuous; sinuous;
insinuating; hence, penetrative or pervasive; -- said of
the mind; its faculties, or its operations; as, a subtle
intellect; a subtle imagination; a subtle process of
thought; also, difficult of apprehension; elusive.
Things remote from use, obscure and subtle.
4. Smooth and deceptive. [Obs.]
Like to a bowl upon a subtle ground [bowling
Syn: Artful; crafty; cunning; shrewd; sly; wily.
Usage: Subtle is the most comprehensive of these epithets and
implies the finest intellectual quality. See Shrewd,