The Collaborative International Dictionary of English v.0.48:

Foil \Foil\ (foil), v. t. [imp. & p. p. Foiled (foild); p. pr.
   & vb. n. Foiling.] [F. fouler to tread or trample under
   one's feet, to press, oppress. See Full, v. t.]
   1. To tread under foot; to trample.
      [1913 Webster]

            King Richard . . . caused the ensigns of Leopold to
            be pulled down and foiled under foot. --Knoless.
      [1913 Webster]

            Whom he did all to pieces breake and foyle,
            In filthy durt, and left so in the loathely soyle.
                                                  --Spenser.
      [1913 Webster]

   2. To render (an effort or attempt) vain or nugatory; to
      baffle; to outwit; to balk; to frustrate; to defeat.
      [1913 Webster]

            And by ? mortal man at length am foiled. --Dryden.
      [1913 Webster]

            Her long locks that foil the painter's power.
                                                  --Byron.
      [1913 Webster]

   3. To blunt; to dull; to spoil; as, to foil the scent in
      chase. --Addison.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Foiling \Foil"ing\, n. (Arch.)
   A foil. --Simmonds.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Foiling \Foil"ing\, n. [Cf. F. foul['e]es. See 1st Foil.]
   (Hunting)
   The track of game (as deer) in the grass.
   [1913 Webster]

WordNet (r) 3.0 (2006):

foiling
    n 1: an act of hindering someone's plans or efforts [syn:
         frustration, thwarting, foiling]