Adjective
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.
Spreading widely, or generally prevailing; affecting great numbers, as an epidemic does; as, epidemic rage; an epidemic evil.
Source: Webster's dictionaryAmong all the diseases of the mind there is not one more epidemical or more pernicious than the love of flattery. Richard Steele