noun / adjective
fanatic
fuh-NAT-ik/fʌnˈætɪk/
A person with extreme, unquestioning devotion to a cause or interest, or showing such devotion.
The fanatic burns books while refusing to reconsider a harmless nature volume.

Etymology
Originally “pertaining to a temple,” Latin fanaticus came to mean divinely inspired or mad. That association with overwhelming religious enthusiasm broadened into excessive, uncritical devotion to a cause.
In context
Leutzenring, a hot-headed fanatic who had spied Jesuits in every corner, and set Nicolae on his journey
More examples
- As a fitness fanatic, she never misses a daily workout.
- His fanatic loyalty to the leader leaves no room for doubt.
- The fanatics dismiss any evidence that challenges their cause.
Forms
fanatic · fanatics
fanaticism noun — Extreme, unquestioning devotion to a cause.
fanatical adjective — Showing extreme, unquestioning enthusiasm or devotion.
Similar words
- zealot
- Especially suggests uncompromising devotion to a religious or political cause.
- enthusiast
- Expresses strong interest without necessarily implying excess or unquestioning devotion.