Ascetic

a. [Gr. ἀσκητικός, from ἀσκεῖν, to exercise, to practice gymnastics.] Unduly rigid in devotions and mortifications; austere. The stern ascetic rigor of the Temple discipline. W. Scott.

n. In the early church, one who retired from the customary business of life, and devoted himself to the duties of piety and devotion; a hermit; a recluse; hence, one who practices undue rigor and self-denial in religious things.

I am far from commending those ascetics that take up their quarters in deserts. Norris.

Ascetic theology, the science which treats of the practice of the theological and moral virtues, and the counsels of perfection. New Am. Cyc.