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.
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
Blunt as the fencer's foils, which hit, but hurt
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.