Enthusiast

Part of speech: noun (n.)

One moved or actuated by enthusiasm; as: (a) One who imagines himself divinely inspired, or possessed of some special revelation; a religious madman; a fanatic. (b) One whose mind is wholly possessed and heated by what engages it; one who is influenced by a peculiar; fervor of mind; an ardent and imaginative person. Enthusiasts soon understand each other. W. Irving.

Synonyms: Visionary; fanatic; devotee; zealot.