What is what does sympathetic mean?

Sympathetic is an adjective that refers to having or showing understanding or compassion for someone else's feelings and experiences. It can also refer to a person or group who supports or agrees with a particular cause or belief. In physiology, sympathetic refers to the part of the autonomic nervous system that activates the "fight or flight" response in response to stress or danger, increasing heart rate, blood pressure, and adrenaline levels.