The Collaborative International Dictionary of English v.0.48:

Philanderer \Phi*lan"der*er\, n.
   One who hangs about women; a male flirt. [R.] --C. Kingsley.
   [1913 Webster]

WordNet (r) 3.0 (2006):

philanderer
    n 1: a man who likes many women and has short sexual
         relationships with them [syn: womanizer, womaniser,
         philanderer]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "philanderer":
   Casanova, Don Juan, Lothario, Romeo, amoroso, beau, boyfriend,
   caballero, cavalier, cavaliere servente, chaser, debauchee,
   esquire, fellow, flame, flirt, gallant, gay deceiver, gay dog,
   gigolo, heartbreaker, inamorato, lady-killer, lecher, libertine,
   love-maker, lover, lover-boy, man, masher, necker, old man, petter,
   philander, playboy, profligate, rake, rakehell, rip, roue, rounder,
   seducer, sheik, skirt chaser, squire, stud, sugar daddy, swain,
   swinger, walking phallus, wanton, wolf, woman chaser, womanizer,
   young man