pen·i·tent / ˈpenitnt/ • adj. feeling or showing sorrow and regret for having done wrong; repentant: a penitent expression.• n. a person who repents their sins or wrongdoings and (in the Christian Church) seeks forgiveness from God. ∎  (in the Roman Catholic Church) a person who confesses their sins to a priest and submits to the penance that he imposes.DERIVATIVES: pen·i·tence n.pen·i·tent·ly adv.

penitent in the Christian Church, a person who confesses their sins to a priest and submits to the penance imposed; originally, this might include the performance of a punishment or discipline as an outward expression or token of repentance for and expiation of a sin. Those doing public penance might wear sackcloth, or (when doing penance for fornication) be dressed in a white sheet.
Penitential Psalms seven psalms (6, 32, 38, 51, 102, 130, 143) which express penitence.