Meaning of “fanatic” - Learner’s Dictionary

fanatic

noun [ C ] uk us /fəˈnætɪk/

someone whose interest in something or enthusiasm for something is extreme:

religious fanatics
fanatical adjective

extremely enthusiastic about something:

She's fanatical about football.
fanaticism uk us /fəˈnætɪsɪzəm/ noun [ U ]

(Definition of “fanatic” from the Cambridge Learner’s Dictionary © Cambridge University Press)