- a person who is filled with enthusiasm for some principle, pursuit, etc.; a person of ardent zeal: a sports enthusiast.
- a religious visionary or fanatic.
- a person filled with or motivated by enthusiasm; fanatic
- archaic a religious visionary, esp one whose zeal for religion is extravagant or unbalanced
1560s, pejorative, “one who believes himself possessed of divine revelations or special communication from God,” from Greek enthousiastes “a person inspired,” from enthousiazein (see enthusiasm). General sense (not always entirely pejorative) is from mid-18c.