A person who holds extreme views, especially one who advocates such views; a radical or fanatic.
Holding extreme views, especially on a political or religious subject.
Of or relating to extremism.
One who believes dogmatically in something regardless of evidence or even conclusive proof that the thing is false or was staged; one who has true-believer syndrome.
Used other than figuratively or idiomatically: see true, believer.
A strict follower of a doctrine.