Refers to a person who strongly believes in and follows a particular ideology, religion, or person. Often used in political, religious, or philosophical contexts.
He is a devoted adherent of that new religion.
That politician has many followers.
Compound of 信奉 (しんぽう, 'belief, faith') and 者 (しゃ, 'person'). 信奉 is itself composed of 信 (しん, 'trust, believe') and 奉 (ほう, 'offer, revere').