a. [ Cf. F. pénitentiaire. ] 1. Relating to penance, or to the rules and measures of penance. “A penitentiary tax.” Abp. Bramhall. [ 1913 Webster ]

2. Expressive of penitence; as, a penitentiary letter. [ 1913 Webster ]

3. Used for punishment, discipline, and reformation. “Penitentiary houses.” Blackstone. [ 1913 Webster ]

n.; pl. Penitentiaries [ Cf. F. pénitencier. See Penitent. ] 1. One who prescribes the rules and measures of penance. [ Obs. ] Bacon. [ 1913 Webster ]

2. One who does penance. [ Obs. ] Hammond. [ 1913 Webster ]

3. A small building in a monastery where penitents confessed. Shpiley. [ 1913 Webster ]

4. That part of a church to which penitents were admitted. Shipley. [ 1913 Webster ]

5. (R. C. Ch.) (a) An office of the papal court which examines cases of conscience, confession, absolution from vows, etc., and delivers decisions, dispensations, etc. Its chief is a cardinal, called the Grand Penitentiary, appointed by the pope. (b) An officer in some dioceses since A. D. 1215, vested with power from the bishop to absolve in cases reserved to him. [ 1913 Webster ]

6. A house of correction, in which offenders are confined for punishment, discipline, and reformation, and in which they are generally compelled to labor; a prison; a jail. Colloquially often shortened to pen. [ 1913 Webster ]

n. The office or condition of a penitentiary of the papal court. [ R. ] Wood. [ 1913 Webster ]