a punishment undergone in token of penitence for sin.

a penitential discipline imposed by church authority.

a sacrament, as in the Roman Catholic Church, consisting in a confession of sin, made with sorrow and with the intention of amendment, followed by the forgiveness of the sin.

noun

absolution , atonement , attrition , compensation , compunction , confession , contrition , expiation , forgiveness , hair shirt , mortification , penalty , penitence , punishment , purgation , remorse , remorsefulness , repentance , retribution , rue , ruth , sackcloth and ashes , self-flagellation , shrift , sorrow , suffering