What is "to run a foil"

Foil \Foil\, n.

1. Failure of success when on the point of attainment; defeat; frustration; miscarriage.
   --Milton.

   Nor e'er was fate so near a foil.
   --Dryden.

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

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

   Isocrates contended with a foil against Demosthenes with a word.
   --Mitford.

3. The track or trail of an animal.

   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.