The Collaborative International Dictionary of English v.0.48:

Villain \Vil"lain\, v. t.
   To debase; to degrade. [Obs.] --Sir T. More.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Villain \Vil"lain\, n. [OE. vilein, F. vilain, LL. villanus,
   from villa a village, L. villa a farm. See Villa.]
   [1913 Webster]
   1. (Feudal Law) One who holds lands by a base, or servile,
      tenure, or in villenage; a feudal tenant of the lowest
      class, a bondman or servant. [In this sense written also
      villan, and villein.]
      [1913 Webster]

            If any of my ansectors was a tenant, and a servant,
            and held his lands as a villain to his lord, his
            posterity also must do so, though accidentally they
            become noble.                         --Jer. Taylor.
      [1913 Webster]

   Note: Villains were of two sorts; villains regardant, that
         is, annexed to the manor (LL. adscripti glebae); and
         villains in gross, that is, annexed to the person of
         their lord, and transferable from one to another.
         --Blackstone.
         [1913 Webster]

   2. A baseborn or clownish person; a boor. [R.]
      [1913 Webster]

            Pour the blood of the villain in one basin, and the
            blood of the gentleman in another, what difference
            shall there be proved?                --Becon.
      [1913 Webster]

   3. A vile, wicked person; a man extremely depraved, and
      capable or guilty of great crimes; a deliberate scoundrel;
      a knave; a rascal; a scamp.
      [1913 Webster]

            Like a villain with a smiling cheek.  --Shak.
      [1913 Webster]

            Calm, thinking villains, whom no faith could fix.
                                                  --Pope.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Villain \Vil"lain\, a. [F. vilain.]
   Villainous. [R.] --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

villain
    n 1: a wicked or evil person; someone who does evil deliberately
         [syn: villain, scoundrel]
    2: the principal bad character in a film or work of fiction
       [syn: villain, baddie]

Moby Thesaurus II by Grady Ward, 1.0:

121 Moby Thesaurus words for "villain":
   Roscius, SOB, actor, actress, antagonist, antihero, bad guy,
   bad person, barnstormer, bastard, bit, bit part, blackguard,
   blighter, bounder, cad, caitiff, cast, character, character actor,
   character man, character woman, child actor, criminal, crook, cue,
   cur, deceiver, delinquent, devil, diseur, diseuse, dog, dramatizer,
   evildoer, fat part, feeder, felon, foil, gangster, heavy, hero,
   heroine, histrio, histrion, ingenue, juvenile, knave, lawbreaker,
   lead, lead role, leading lady, leading man, leading woman, lines,
   malefactor, malevolent, malfeasant, malfeasor, matinee idol, mime,
   mimer, mimic, miscreant, misfeasor, mobster, monologist, mummer,
   outlaw, pantomime, pantomimist, part, person, personage, piece,
   playactor, player, precious rascal, protagonist, protean actor,
   public enemy, racketeer, rapscallion, rascal, rat, reciter,
   reptile, rogue, role, rotter, scalawag, scamp, scoundrel, shyster,
   side, sinner, sneak, soubrette, spalpeen, stage performer,
   stage player, stooge, straight man, straight part, stroller,
   strolling player, supporting character, supporting role,
   theatrical, thespian, thief, title role, transgressor, trouper,
   utility man, viper, walk-on, walking part, worker of ill, wretch,
   wrongdoer



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

VILLAIN., An epithet used to cast contempt and contumely on the person to
whom it is applied.
     2. To call a man a villain in a letter written to a third person, will
entitle him to an action without proof of special damages. 1 Bos. & Pull.
331.