Practitioner of rigorous penance- When one (an ascetic) practices a definite course of penance such as fasting for one day, or two days and so on up to one month, for the whole life, such practitioner is called Ugratapa.
caturthaṣaṣṭhāstamadaśamadvādaśapaksamāsadyanaśanayogesvanyatamayogamārabhya āmaraṇādanivartakā ugratapasaḥ.
(Ta Vā 3.36)