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]

WordNet (r) 3.0 (2006):

foiled
    adj 1: disappointingly unsuccessful; "disappointed expectations
           and thwarted ambitions"; "their foiled attempt to capture
           Calais"; "many frustrated poets end as pipe-smoking
           teachers"; "his best efforts were thwarted" [syn:
           defeated, disappointed, discomfited, foiled,
           frustrated, thwarted]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "foiled":
   baffled, balked, betrayed, bilked, blasted, blighted, chapfallen,
   crestfallen, crossed, crushed, dashed, defeated, disappointed,
   dished, disillusioned, dissatisfied, frustrated, ill done-by,
   ill-served, let down, out of countenance, regretful,
   sorely disappointed, soured, thwarted