Ascetic

Webster's Dictionary

(1): (n.) In the early church, one who devoted himself to a solitary and contemplative life, characterized by devotion, extreme self-denial, and self-mortification; a hermit; a recluse; hence, one who practices extreme rigor and self-denial in religious things.

(2): (a.) Extremely rigid in self-denial and devotions; austere; severe.

Charles Buck Theological Dictionary

One who retires from the world for the purpose of devotion and mortification. When the monks came in fashion, this title was bestowed upon them, especially such as lived in solitude. It was also the title of several books of spiritual exercises, as the Ascetics, or devout exercises of St. Basil, &c.