1. Difficult to notice or understand:
* Example: "There was a subtle change in her mood."
2. Delicate or refined:
* Example: "The artist used subtle shades of color."
3. Not obvious or direct:
* Example: "He made a subtle hint that he was leaving."
4. Having a delicate or understated flavor:
* Example: "This wine has a subtle oaky flavor."
5. (In art or music) characterized by a refined, understated, or complex use of form and technique:
* Example: "The painting is a masterpiece of subtle composition."
In essence, something subtle is like a whisper in a crowded room - it's there, but you have to pay attention to notice it.