true believer

American  

noun

1. a person who has been thoroughly convinced of something.

2. a fanatic, especially a religious or political one.

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Example Sentences

"It was at that point that I became a true believer, not only because it was morally wrong, but ... because I'm a fighter," he said.

From Reuters

Somerhalder seems like a true believer in the cause.

From Slate

In the end, Watt was undone by the arrogance of the true believer.

From Los Angeles Times

I think DeSantis is indeed a true believer.

From Salon

Gabe was a true believer in Arete.

From Slate