adjective

1. of, expressing, resulting from, feeling, or showing sympathy; sympathizing
2. in agreement with one's tastes, mood, feelings, disposition, etc.; congenial
3. showing favor, approval, or agreement to be sympathetic to a plan
4. Physiol. designating or of that part of the autonomic nervous system whose nerves originate in the lumbar and thoracic regions of the spinal cord and that is especially concerned with mediating the involuntary response to alarm, as by speeding the heart rate, raising the blood pressure, and dilating the pupils of the eyes: these nerves oppose the parasympathetic nerves in the regulation of many body processes
5. Physics, Acoustics designating or of vibrations, sounds, etc. caused by other vibrations of the same period transmitted from a neighboring vibrating body

Etymology: ModL sympatheticus < Gr sympatheia, sympathy, infl. by Gr pathētikos, pathetic