The Collaborative International Dictionary of English v.0.48:

Swinger \Swing"er\, n.
   One who swings or whirls.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Swinger \Swin"ger\, n.
   1. One who swinges.
      [1913 Webster]

   2. Anything very large, forcible, or astonishing. [Obs. or
      Colloq.] --Herrick.
      [1913 Webster]

WordNet (r) 3.0 (2006):

swinger
    n 1: someone who swings sports implements
    2: a person who engages freely in promiscuous sex [syn:
       swinger, tramp]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "swinger":
   Beau Brummel, Bohemian, Casanova, Don Juan, Lothario,
   arbiter of fashion, beatnik, clotheshorse, clubman, clubwoman,
   dandy, deb, debauchee, debutante, deviant, dissenter, dropout,
   fashion plate, fashionable, flower child, fop, freak, gallant,
   gay deceiver, gay dog, heretic, hippie, lady-killer, libertine,
   lover-boy, man-about-town, maverick, misfit, mondain, mondaine,
   nonconformist, nonjuror, original, philanderer, profligate, rake,
   rakehell, rip, roue, rounder, sectarian, sectary, skirt chaser,
   socialite, subdeb, subdebutante, taste-maker, tone-setter,
   trend-setter, ugly duckling, unconformist, walking phallus, wanton,
   wolf, woman chaser, womanizer, yippie