1. difficult to notice or understand; not obvious
2. skillfully made or done in a way that is not immediately apparent
3. having or showing skill at recognizing or understanding things that are not obvious

Examples

• There was a subtle change in her tone of voice.
• The painting uses subtle shades of blue and green.
• His subtle humor often went unnoticed by others.
• She made a subtle hint about wanting to leave early.
• The chef added subtle flavors that enhanced the dish.
• He has a subtle understanding of human nature.
• The difference between the two products is quite subtle.