Adjective

(en adjective)

Performed with, or characterized by, art or skill.

Artificial; imitative.

Using or exhibiting much art, skill, or contrivance; dexterous; skillful.

Cunning; disposed to cunning indirectness of dealing; crafty; as, an artful boy. [The usual sense.]

*{{quote-news, year=2012

, date=June 29 , author=Kevin Mitchell , title=Roger Federer back from Wimbledon 2012 brink to beat Julien Benneteau , work=the Guardian citation , page= , passage=Where the Czech upstart Rosol, ranked 100 in the world, all but blew Nadal's head off with his blunderbuss in a fifth set of unrivalled intensity on Thursday night, Benneteau, a more artful citizen, used a rapier to hurt his vaunted foe before falling just short of a kill. In the end, it was he who staggered from the scene of the fight. }}

Adjective

(er)

Hard to grasp; not obvious or easily understood; barely noticeable.

The difference is subtle , but you can hear it if you listen carefully.

(of a thing) Cleverly contrived.

(of a person or animal) Cunning, skillful.

insidious

* 1623 , , act iv, scene 4,

Thy age confirmed, proud, subtle , bloody, treacherous.

Tenuous; rarefied; of low density or thin consistency.