penitential

adjective

1. of, pertaining to, proceeding from, or expressive of penitence or repentance.

noun

2. a penitent.
3. a book or code of canons relating to penance, its imposition, etc.

adjective

1. of, showing, or constituting penance

noun

2. mainly RC Church a book or compilation of instructions for confessors
3. a less common word for penitent (def. 2), penitent (def. 3)

adj.c.1500, from Medieval Latin penitentialis, from Latin paenitentia “repentance” (see penitence).