Emily Dickinson Lexicon

EP-I-DEM'IC, or EP-I-DEM'IC-AL, a. [Gr. επι and δημος, people.]

1. Common to many people. An epidemic disease is one which, independent of local cause, seizes a great number of people, at the same time, or in the same season. Thus we speak of epidemic fever; epidemic catarrh. It is used in distinction from endemic.
2. Generally prevailing; affecting great numbers; as, epidemic rage; an epidemic evil.