The Collaborative International Dictionary of English v.0.48:

Casanova \Casanova\ n.
   1. an Italian adventurer (Giovanni Giacomo Casanova; b. 1725;
      d. 1798) who wrote vivid accounts of his sexual
      encounters.
      [WordNet 1.5]

   2. any man noted for his amorous adventures.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

Casanova
    n 1: an Italian adventurer who wrote vivid accounts of his
         sexual encounters (1725-1798) [syn: Casanova, Giovanni
         Jacopo Casanova, Casanova de Seingalt, Giovanni Jacopo
         Casanova de Seingalt]
    2: any man noted for his amorous adventures

Moby Thesaurus II by Grady Ward, 1.0:

92 Moby Thesaurus words for "Casanova":
   Artful Dodger, Don Juan, Lothario, Machiavel, Machiavelli,
   Machiavellian, Romeo, actor, amoroso, bamboozler, beau, befuddler,
   beguiler, boyfriend, caballero, cavalier, cavaliere servente,
   charmer, chaser, counterfeiter, debauchee, deceiver, deluder,
   dissembler, dissimulator, dodger, double-dealer, duper, enchanter,
   entrancer, esquire, faker, fellow, flame, fooler, forger, gallant,
   gay deceiver, gay dog, gigolo, hoaxer, hypnotizer, inamorato, jilt,
   jilter, joker, jokester, kidder, lady-killer, leg-puller,
   libertine, lothario, love-maker, lover-boy, man, masher,
   mesmerizer, misleader, necker, old man, paramour, petter,
   philander, philanderer, plagiarist, plagiarizer, playactor,
   practical joker, profligate, ragger, rake, rakehell, rip,
   role-player, roue, rounder, seducer, sheik, skirt chaser, spoofer,
   squire, sugar daddy, swain, swinger, tease, teaser,
   walking phallus, wanton, wolf, woman chaser, womanizer,
   young man