The Collaborative International Dictionary of English v.0.48:

Swain \Swain\, n. [OE. swain, swein, Icel. sveinn a boy,
   servant; akin to Sw. sven, Dan. svend, AS. sw[=a]n, OHG.
   swein.]
   1. A servant. [Obs.]
      [1913 Webster]

            Him behoves serve himself that has no swain.
                                                  --Chaucer.
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   2. A young man dwelling in the country; a rustic; esp., a
      cuntry gallant or lover; -- chiefly in poetry.
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            It were a happy life
            To be no better than a homely swain.  --Shak.
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            Blest swains! whose nymphs in every grace excel.
                                                  --Pope.
      [1913 Webster]

WordNet (r) 3.0 (2006):

swain
    n 1: a man who is the lover of a girl or young woman; "if I'd
         known he was her boyfriend I wouldn't have asked" [syn:
         boyfriend, fellow, beau, swain, young man]