The Collaborative International Dictionary of English v.0.48:

Criminal \Crim"i*nal\ (kr?m"?-nal), a. [L. criminalis, fr.
   crimen: cf. F. criminel. See Crime.]
   1. Guilty of crime or sin.
      [1913 Webster]

            The neglect of any of the relative duties renders us
            criminal in the sight of God.         --Rogers.
      [1913 Webster]

   2. Involving a crime; of the nature of a crime; -- said of an
      act or of conduct; as, criminal carelessness.
      [1913 Webster]

            Foppish and fantastic ornaments are only indications
            of vice, not criminal in themselves.  --Addison.
      [1913 Webster]

   3. Relating to crime; -- opposed to civil; as, the criminal
      code.
      [1913 Webster]

            The officers and servants of the crown, violating
            the personal liberty, or other right of the subject
            . . . were in some cases liable to criminal process.
                                                  --Hallam.
      [1913 Webster]

   Criminal action (Law), an action or suit instituted to
      secure conviction and punishment for a crime.

   Criminal conversation (Law), unlawful intercourse with a
      married woman; adultery; -- usually abbreviated, crim.
      con.

   Criminal law, the law which relates to crimes.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Criminal \Crim"i*nal\, n.
   One who has commited a crime; especially, one who is found
   guilty by verdict, confession, or proof; a malefactor; a
   felon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

criminal
    adj 1: bringing or deserving severe rebuke or censure; "a
           criminal waste of talent"; "a deplorable act of
           violence"; "adultery is as reprehensible for a husband as
           for a wife" [syn: condemnable, criminal,
           deplorable, reprehensible, vicious]
    2: guilty of crime or serious offense; "criminal in the sight of
       God and man"
    3: involving or being or having the nature of a crime; "a
       criminal offense"; "criminal abuse"; "felonious intent" [syn:
       criminal, felonious]
    n 1: someone who has committed a crime or has been legally
         convicted of a crime [syn: criminal, felon, crook,
         outlaw, malefactor]

Moby Thesaurus II by Grady Ward, 1.0:

211 Moby Thesaurus words for "criminal":
   Judas, Mafioso, aberrant, abnormal, abominable, actionable,
   against the law, amoral, anarchic, anarchistic, anomic,
   arraignable, arrant, at fault, atrocious, bad, bad guy, bad person,
   base, betrayer, black, black-market, blackguard, blamable,
   blameworthy, bootleg, censurable, chargeable, conscienceless,
   contraband, contrary to law, convict, corrupt, corrupted, crook,
   crooked, culpable, culprit, damnable, dark, deceiver, delinquent,
   depraved, desperado, desperate criminal, deviant, devious,
   disgraceful, dishonest, dishonorable, double-dealer, doubtful,
   dubious, evasive, evil, evildoer, evildoing, execrable, faulty,
   felon, felonious, fishy, flagitious, flagrant, flawed, foul,
   fraudulent, fugitive, gallows bird, gangster, gaolbird, guilty,
   hardly the thing, heinous, hood, hoodlum, hooligan, ignominious,
   ill-got, ill-gotten, illegal, illegitimate, illicit, immoral,
   impeachable, impermissible, implicated, improper, inappropriate,
   incorrect, inculpated, indecorous, indictable, indirect, infamous,
   iniquitous, insidious, involved, irregular, jailbird, justiciable,
   knave, knavish, lawbreaker, lawless, low, malefactor, malefactory,
   malevolent, malfeasant, malfeasor, miscreant, misfeasor, mobster,
   monstrous, naughty, nefarious, nonconstitutional, nonlegal,
   nonlicit, not done, not kosher, not the thing, off-base, off-color,
   offender, out-of-line, outlaw, outlawed, peccant, public enemy,
   punishable, questionable, quisling, racketeer, rank, reprehensible,
   reproachable, reprobate, reprovable, rotten, roughneck, ruffian,
   sacrilegious, scandalous, scofflaw, scoundrel, shady, shameful,
   shameless, shifty, sinful, sinister, sinner, slippery, suspicious,
   swindler, terrible, terrorist, thief, thug, to blame, tough,
   traitor, transgressor, trespasser, triable, tricky, two-timer,
   unallowed, unauthorized, unconscienced, unconscientious,
   unconscionable, unconstitutional, under-the-counter,
   under-the-table, underhand, underhanded, undue, unethical, unfit,
   unfitting, unforgivable, unlawful, unofficial, unpardonable,
   unprincipled, unrighteous, unsavory, unscrupulous, unseemly,
   unspeakable, unstatutory, unstraightforward, unsuitable,
   unwarrantable, unwarranted, unworthy, vicious, vile, villain,
   villainous, wicked, without remorse, without shame, worker of ill,
   wrong, wrongdoer, wrongdoing, wrongful



Bouvier's Law Dictionary, Revised 6th Ed (1856):

CRIMINAL. Relating to, or having the character of crime; as, criminal law,
criminal conversation, &c. It also signifies a person convicted of a crime.