na-adjective
fanatic; fanatical
Describes extreme, uncritical devotion to a belief, cause, or person. Often carries a negative connotation of irrational zeal.
彼は狂信的な愛国者だ。
He is a fanatical patriot.
その教団の狂信的な信者たちは、外
The cult's fanatical followers had cut off contact with the outside world.
Compound of 狂信 (kyōshin, 'fanatic belief') + 的 (-teki, '-like, -ical'). 狂信 itself is from 狂 (kyō, 'mad, insane') and 信 (shin, 'belief, faith').