The Collaborative International Dictionary of English v.0.48:

Foil \Foil\, n.
   1. Failure of success when on the point of attainment;
      defeat; frustration; miscarriage. --Milton.
      [1913 Webster]

            Nor e'er was fate so near a foil.     --Dryden.
      [1913 Webster]

   2. A blunt weapon used in fencing, resembling a smallsword in
      the main, but usually lighter and having a button at the
      point.
      [1913 Webster]

            Blunt as the fencer's foils, which hit, but hurt
            not.                                  --Shak.
      [1913 Webster]

            Isocrates contended with a foil against Demosthenes
            with a word.                          --Mitford.
      [1913 Webster]

   3. The track or trail of an animal.
      [1913 Webster]

   To run a foil,to lead astray; to puzzle; -- alluding to the
      habits of some animals of running back over the same track
      to mislead their pursuers. --Brewer.
      [1913 Webster]