Source : Webster's Revised Unabridged Dictionary (1913)

Infamous \In"fa*mous\, a. [Pref. in- not + famous: cf. L.
   infamis. See {Infamy}.]
   1. Of very bad report; having a reputation of the worst kind;
      held in abhorrence; guilty of something that exposes to
      infamy; base; notoriously vile; detestable; as, an
      infamous traitor; an infamous perjurer.

            False errant knight, infamous, and forsworn.
                                                  --Spenser.

   2. Causing or producing infamy; deserving detestation;
      scandalous to the last degree; as, an infamous act;
      infamous vices; infamous corruption. --Macaulay.

   3. (Law) Branded with infamy by conviction of a crime; as, at
      common law, an infamous person can not be a witness.

   4. Having a bad name as being the place where an odious crime
      was committed, or as being associated with something
      detestable; hence, unlucky; perilous; dangerous.
      ``Infamous woods.'' --P. Fletcher.

            Infamous hills, and sandy perilous wilds. --Milton.

            The piny shade More infamous by cursed Lycaon made.
                                                  --Dryden.

   Syn: Detestable; odious; scandalous; disgraceful; base; vile;
        shameful; ignominious.

Source : WordNet®

infamous
     adj : having an exceedingly bad reputation; "a notorious
           gangster"; "the tenderloin district was notorious for
           vice" [syn: {ill-famed}, {notorious}]