The Collaborative International Dictionary of English v.0.48:

Infamy \In"fa*my\, n.; pl. Infamies. [L. infamia, fr. infamis
   infamous; pref. in- not + fama fame: cf. F. infamie. See
   Fame.]
   [1913 Webster]
   1. Total loss of reputation; public disgrace; dishonor;
      ignominy; indignity.
      [1913 Webster]

            The afflicted queen would not yield, and said she
            would not . . . submit to such infamy. --Bp. Burnet.
      [1913 Webster]

   2. A quality which exposes to disgrace; extreme baseness or
      vileness; as, the infamy of an action.
      [1913 Webster]

   3. (Law) That loss of character, or public disgrace, which a
      convict incurs, and by which he is at common law rendered
      incompetent as a witness.
      [1913 Webster]

            Yesterday, Dec. 7, 1941 -- a day which will live in
            infamy, . . .                         --Franklin D.
                                                  Roosevelt.

WordNet (r) 3.0 (2006):

infamy
    n 1: a state of extreme dishonor; "a date which will live in
         infamy"- F.D.Roosevelt; "the name was a by-word of scorn
         and opprobrium throughout the city" [syn: infamy,
         opprobrium] [ant: celebrity, fame, renown]
    2: evil fame or public reputation [ant: fame]

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "infamy":
   abhorrence, abomination, atrocity, bad, degradation, demotion,
   depluming, desecration, detestation, discredit, disesteem,
   disgrace, disgracefulness, dishonor, displuming, disrepute,
   egregiousness, error, evil, hatred, heinousness, ignobility,
   ignominiousness, ignominy, ill fame, ill repute, infamousness,
   ingloriousness, iniquity, knavery, loathsomeness, loss of honor,
   monstrosity, notoriety, notoriousness, obliquity, obloquy, odium,
   opprobrium, outrage, peccancy, pity, profanation, reprobacy,
   revulsion, sacrilege, scandal, shame, shamefulness, sin, stigma,
   terrible thing, vileness, villainy, violation, wickedness, wrong



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

INFAMY, crim. law, evidence. That state which is produced by the conviction
of crime and the loss of honor, which renders the infamous person
incompetent as a witness.
     2. It is to be considered, 1st. What crimes or punishment incapacitate
a witness. 2d. How the guilt is to be proved. 3d. How the objection
answered. 4th. The effect of infamy.
     3.-1. When a man is convicted of an offence which is inconsistent
with the common principles of honesty and humanity, the law considers his
oath to be of no weight, and excludes his testimony as of too doubtful and
suspicious a nature to be admitted in a court of justice to deprive another
of life, liberty or property. Gilb. L. E. 256; 2 Bulst. 154; 1 Phil. 23;
Bull. N. P. 291. The crimes which render a person incompetent, are treason;
5 Mod. 16, 74; felony; 2 Bulst. 154; Co. Litt. 6; T. Raym. 369; all offences
founded in fraud, and which come within the general. notion of the crimen
falsi of the Roman law; Leach, 496; as perjury and forgery; Co. Litt. 6;
Fort. 209; piracy 2 Roll. Ab. 886; swindling, cheating; Fort. 209; barratry;
2 Salk. 690; and the bribing a witness to absent himself from a trial, in
order to get rid of his evidence. Fort. 208. It is the crime and not the
punishment which renders the offender unworthy of belief. 1 Phill. Ev. 25.
     4.-2. In order to incapacitate the party, the judgment must be proved
as pronounced by a court possessing competent jurisdiction. 1 Sid. 51; 2
Stark. C. 183; Stark. Ev. part 2, p. 144, note 1; Id. part 4, p. 716. But it
has been held that a conviction of an infamous crime in another country, or
another of the United States, does not render the witness incompetent on the
ground of infamy. 17 Mass. 515. Though this doctrine appears to be at
variance with the opinions entertained by foreign jurists, who maintain that
the state or condition of a person in the place of his domicil accompanies
him everywhere. Story, Confl. Sec. 620, and the authorities there cited;
Foelix, Traite De Droit Intern. Prive, 31; Merl. Repert, mot Loi, Sec. 6, n.
6.
     5.-3. The objection to competency may be answered, 1st. By proof of
pardon. See Pardon. And, 2d. By proof of a reversal by writ of error, which
must be proved by the production of the record.
     6.-4. The judgment for an infamous crime, even for perjury, does not
preclude the party from making an affidavit with a view to his own defence.
2 Salk. 461 2 Str. 1148; Martin's Rep. 45. He may, for instance, make an
affidavit in relation to the irregularity of a judgment in a cause in which
he, is a party, for otherwise he would be without a remedy. But the rule is
confined to defence, and he cannot be heard upon oath as complainant. 2
Salk. 461 2 Str. 1148. When the witness becomes incompetent from infamy of
character, the effect is the same as if he were dead and if he has attested
any instrument as a witness, previous to his conviction, evidence may be
given of his handwriting. 2 Str. 833; Stark. Ev. part. 2, sect. 193; Id.
part 4, p. 723.
     7. By infamy is also understood the expressed opinion of men generally
as to the vices of another. Wolff, Dr. de la Nat. et des Gens, Sec. 148.