(adj) (especially of medicine) of disease or anything resembling a disease; attacking or affecting many individuals in a community or a population simultaneously, Ant. endemic, ecdemic, Example:an epidemic outbreak of influenza
{ } a. [ L. epidemus, Gr. &unr_;, &unr_;, among the people, epidemic; &unr_; in + &unr_; people: cf. F. épidémique. Cf. Demagogue. ] 1. (Med.) Common to, or affecting at the same time, a large number in a community; -- applied to a disease which, spreading widely, attacks many persons at the same time; as, an epidemic disease; an epidemic catarrh, fever, etc. See Endemic. [ 1913 Webster ]
2. Spreading widely, or generally prevailing; affecting great numbers, as an epidemic does; as, epidemic rage; an epidemic evil. [ 1913 Webster ]
It was the epidemical sin of the nation. Bp. Burnet. [ 1913 Webster ]