The Collaborative International Dictionary of English v.0.48:

Libertine \Lib"er*tine\ (-t[i^]n), n. [L. libertinus freedman,
   from libertus one made free, fr. liber free: cf. F. libertin.
   See Liberal.]
   1. (Rom. Antiq.) A manumitted slave; a freedman; also, the
      son of a freedman.
      [1913 Webster]

   2. (Eccl. Hist.) One of a sect of Anabaptists, in the
      fifteenth and early part of the sixteenth century, who
      rejected many of the customs and decencies of life, and
      advocated a community of goods and of women.
      [1913 Webster]

   3. One free from restraint; one who acts according to his
      impulses and desires; now, specifically, one who gives
      rein to lust; a rake; a debauchee.
      [1913 Webster]

            Like a puffed and reckless libertine,
            Himself the primrose path of dalliance treads.
                                                  --Shak.
      [1913 Webster]

   4. A defamatory name for a freethinker. [Obsolescent]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Libertine \Lib"er*tine\, a. [L. libertinus of a freedman: cf. F.
   libertin. See Libertine, n. ]
   1. Free from restraint; uncontrolled. [Obs.]
      [1913 Webster]

            You are too much libertine.           --Beau. & Fl.
      [1913 Webster]

   2. Dissolute; licentious; profligate; loose in morals; as,
      libertine principles or manners. --Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

libertine
    adj 1: unrestrained by convention or morality; "Congreve draws a
           debauched aristocratic society"; "deplorably dissipated
           and degraded"; "riotous living"; "fast women" [syn:
           debauched, degenerate, degraded, dissipated,
           dissolute, libertine, profligate, riotous,
           fast]
    n 1: a dissolute person; usually a man who is morally
         unrestrained [syn: libertine, debauchee, rounder]

Moby Thesaurus II by Grady Ward, 1.0:

89 Moby Thesaurus words for "libertine":
   Casanova, Don Juan, Lothario, Paphian, adulterer, amoral, bestial,
   broad-minded, carnal, debauched, debauchee, debaucher, decadent,
   degenerate, depraved, dirty, dirty old man, dissolute, fast,
   filthy, fornicator, free lance, free spirit, free trader,
   freethinker, freethinking, gallant, gay deceiver, gay dog, goatish,
   heartbreaker, hircine, horny, immoral, incontinent, independent,
   individualist, isolationist, lady-killer, lascivious,
   latitudinarian, lecher, lecherous, lewd, liberal, libertarian,
   libidinous, licentious, lover-boy, lubricious, lubricous, lustful,
   masher, mugwump, neutral, nonpartisan, old goat, open-minded,
   philander, philanderer, philandering, profligate, prurient, rake,
   rakehell, rakish, randy, reprobate, rip, roue, rounder,
   rugged individualist, ruttish, salacious, satyric, satyrical,
   seducer, skirt chaser, swinger, third force, third world, tolerant,
   unbigoted, walking phallus, wanton, whoremonger, wolf,
   woman chaser, womanizer



Easton's 1897 Bible Dictionary:

Libertine
   found only Acts 6:9, one who once had been a slave, but who had
   been set at liberty, or the child of such a person. In this case
   the name probably denotes those descendants of Jews who had been
   carried captives to Rome as prisoners of war by Pompey and other
   Roman generals in the Syrian wars, and had afterwards been
   liberated. In A.D. 19 these manumitted Jews were banished from
   Rome. Many of them found their way to Jerusalem, and there
   established a synagogue.