Subtile

Sub"tile (?), a. [L. subtilis. See Subtile.] 1. Thin; not dense or gross; rare; as, subtile air; subtile vapor; a subtile medium.

2. Delicately constituted or constructed; nice; fine; delicate; tenuous; finely woven. "A sotil [subtile] twine's thread." Chaucer.

More subtile web Arachne can not spin.
Spenser.

I do distinguish plain
Each subtile line of her immortal face.
Sir J. Davies.

3. Acute; piercing; searching.

The slow disease and subtile pain.
Prior.

5. Characterized by nicety of discrimination; discerning; delicate; refined; subtle. [In this sense now commonly written subtle.]

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.

The subtile influence of an intellect like Emerson's.
Hawthorne.

5. Sly; artful; cunning; crafty; subtle; as, a subtile person; a subtile adversary; a subtile scheme. [In this sense now commonly written subtle.]

Syn. -- Subtile, Acute. In acute the image is that of a needle's point; in subtile that of a thread spun out to fineness. The acute intellect pierces to its aim; the subtile (or subtle) intellect winds its way through obstacles.

-- Sub"tile*ly, adv. -- Sub"tile*ness, n.