/ ɪnˈθjuːziæst; NAmE -ˈθuː-/ noun enthusiast (for / of sth)
1.
a person who is very interested in sth and spends a lot of time doing it :
a football enthusiast
an enthusiast of jazz
2.
a person who approves of sth and shows enthusiasm for it :
enthusiasts for a united Europe
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WORD ORIGIN
early 17th cent. (denoting a person believing that he or she is divinely inspired): from French enthousiaste or ecclesiastical Latin enthusiastes member of a heretical sect, from Greek enthousiastēs person inspired by a god, from the adjective enthous possessed by a god, inspired (based on theos god).