Sŭb'tile, a.
a. [Lat. subtilis, from prefix sub, under, somewhat, slightly, and tela, a web, warp, and therefore properly woven fine; Fr., O. Sp., & Pg. subtil, Pr. subtil, subtil, sotil, Sp. sutil, It. sottile.]
Sense 1. Thin; not dense or gross; rare; as, subtile air; subtile vapor; a subtile medium.
Sense 2. Delicately constituted or constructed; nice; fine; delicate.
More subtile web Arachne can not spin. Spenser.
I do distinguish plain Each subtile line of her immortal face. Davies.
Sense 3. Acute; piercing; as, subtile pain. Prior.
Sense 4. Characterized by acuteness of mind; refined; shrewd; discerning; as, a subtile understanding or argument.
Sense 5. Sly; artful; cunning; crafty; insinuating; as, a subtile person; a subtile adversary; a subtile scheme.
☞ In the last two senses, more commonly written subtle.
Synonyms—Acute; shrewd; artful; cunning.—SUBTILE, ACUTE. In acute the image is that of a needle's point; in subtile that of a thread spun out to extreme fineness. Hence, he who is acute has a piercing judgment, which enables him to discern and discriminate with the nicest accuracy; he who has a subtile intellect can spin the finest thread of thought, and follow out a subject in its most complicated relations, without letting go his hold, or becoming lost or perplexed in its utmost intricacies. Acuteness guards against error; subtilty carries forward our investigations into tenuous and recondite truths. The former belongs more to speculative and abstract inquiries; the latter to the philosophy of the heart and of social life. Edwards was singularly acute; Lord Bacon had a subtilty of intellect which seemed to spread itself throughout every part of a subject like a kind of “diffusive touch.” “The genius of the Spanish people is exquisitely subtile, without being at all acute; hence there is so much humor and so little wit in their literature. The genius of the Italians, on the contrary, is acute, profound, and sensual, but not subtile; hence what they think to be humorous, is merely witty.” Coleridge.