Pronunciation: (ep"i-dem'ik),[key] —adj. 1. Also,ep"i•dem'i•cal.(of a disease) affecting many persons at the same time, and spreading from person to person in a locality where the disease is not permanently prevalent.
2. extremely prevalent; widespread.
—n. 1. a temporary prevalence of a disease.
2. a rapid spread or increase in the occurrence of something: an epidemic of riots.