A fad is a practice or interest followed for a time with exaggerated zeal. Fad or FAD may also refer to: Familial Alzheimer disease, an uncommon form of Alzheimer's disease Flavin adenine dinucleotide is a redox cofactor chemical compound. Fad Browne (1906–1991), Irish politician Fad diet First appearance datum, the date of the oldest known fossil of a living species Fish aggregating device, for fishing Flying Ant Day, a period of increased perception of the nuptial flight for ants prompted by changes in weather. Wagi language of Papua New Guinea, ISO 639-3 code Food availability decline; see Theories of famines Fusil Automático Doble, a rifle used by the Peruvian Army. See also FADD Fads (disambiguation)