Meaning

• 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.

• Tenuous; rarefied; of low density or thin consistency.

• Refined; exquisite.