Source : Webster's Revised Unabridged Dictionary (1913)

Attainder \At*tain"der\, n. [OF. ataindre, ateindre, to accuse,
   convict. Attainder is often erroneously referred to F.
   teindre tie stain. See {Attaint}, {Attain}.]
   1. The act of attainting, or the state of being attainted;
      the extinction of the civil rights and capacities of a
      person, consequent upon sentence of death or outlawry; as,
      an act of attainder. --Abbott.

   Note: Formerly attainder was the inseparable consequence of a
         judicial or legislative sentence for treason or felony,
         and involved the forfeiture of all the real and
         personal property of the condemned person, and such
         ``corruption of blood'' that he could neither receive
         nor transmit by inheritance, nor could he sue or
         testify in any court, or claim any legal protection or
         rights. In England attainders are now abolished, and in
         the United States the Constitution provides that no
         bill of attainder shall be passed; and no attainder of
         treason (in consequence of a judicial sentence) shall
         work corruption of blood or forfeiture, except during
         the life of the person attainted.

   2. A stain or staining; state of being in dishonor or
      condemnation. [Obs.]

            He lived from all attainder of suspect. --Shak.

   {Bill of attainder}, a bill brought into, or passed by, a
      legislative body, condemning a person to death or
      outlawry, and attainder, without judicial sentence.

Source : WordNet®

bill of attainder
     n : a legislative act finding a person guilty of treason or
         felony without a trial; "bills of attainder are
         prohibited by the Constitution of the United States"