Source : Webster's Revised Unabridged Dictionary (1913)

Penal \Pe"nal\, a. [L. poenalis, fr. poena punishment: cf. F.
   p['e]nal. See {Pain}.]
   Of or pertaining to punishment, to penalties, or to crimes
   and offenses; pertaining to criminal jurisprudence: as:
   (a) Enacting or threatening punishment; as, a penal statue;
       the penal code.
   (b) Incurring punishment; subject to a penalty; as, a
       penalact of offense.
   (c) Inflicted as punishment; used as a means of punishment;
       as, a penal colony or settlement. ``Adamantine chains and
       penal fire.'' --Milton.

   {Penal code} (Law), a code of laws concerning crimes and
      offenses and their punishment.

   {Penal laws}, {Penal statutes} (Law), laws prohibited certain
      acts, and imposing penalties for committing them.

   {Penal servitude}, imprisonment with hard labor, in a prison,
      in lieu of transportation. [Great Brit.]

   {Penal suit}, {Penal action} (Law), a suit for penalties.

Source : WordNet®

penal
     adj 1: of or relating to punishment; "penal reform"; "penal code"
     2: serving as or designed to impose punishment; "penal
        servitude"; "a penal colony"
     3: subject to punishment by law; "a penal offense" [syn: {punishable}]