Webster's Revised Unabridged Dictionary · 1913

Penitential

Penitential , adjective

[Compare French pénitentiel.]

Of or pertaining to penitence, or to penance; expressing penitence; of the nature of penance; as, the penitential book; penitential tears.
Penitential stripes. — Cowper
Guilt that all the penitential fires of hereafter can not cleanse. — Sir W. Scott

Penitential , noun

(Roman Catholic Church) A book formerly used by priests hearing confessions, containing rules for the imposition of penances; -- called also penitential book.