The Collaborative International Dictionary of English v.0.48:

Light-o'-love \Light"-o'-love`\ (l[imac]t"[-o]-l[u^]v`), n.
   1. An old tune of a dance, the name of which made it a
      proverbial expression of levity, especially in love
      matters. --Nares. "Best sing it to the tune of
      light-o'-love." --Shak.
      [1913 Webster]

   2. Hence: A light or wanton woman; a woman inconstant in
      love. Called also light-of-love. --Beau. & Fl.
      [1913 Webster]

WordNet (r) 3.0 (2006):

light-of-love
    n 1: a woman inconstant in love [syn: light-o'-love, light-
         of-love]