a. [ L. subtilis. See Subtile. ] 1. Thin; not dense or gross; rare; as, subtile air; subtile vapor; a subtile medium. [ 1913 Webster ]

2. Delicately constituted or constructed; nice; fine; delicate; tenuous; finely woven. “A sotil [ subtile ] twine's thread.” Chaucer. [ 1913 Webster ]

More subtile web Arachne can not spin. Spenser. [ 1913 Webster ]

I do distinguish plain
Each subtile line of her immortal face. Sir J. Davies. [ 1913 Webster ]

3. Acute; piercing; searching. [ 1913 Webster ]

The slow disease and subtile pain. Prior. [ 1913 Webster ]

5. Characterized by nicety of discrimination; discerning; delicate; refined; subtle. [ In this sense now commonly written subtle. ] [ 1913 Webster ]

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. [ 1913 Webster ]

The subtile influence of an intellect like Emerson's. Hawthorne. [ 1913 Webster ]

5. Sly; artful; cunning; crafty; subtle; as, a subtile person; a subtile adversary; a subtile scheme. [ In this sense now commonly written subtle. ] [ 1913 Webster ]

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. [ 1913 Webster ]

-- Sub"tile*ly, adv. -- Sub"tile*ness, n. [ 1913 Webster ]