foil - Dictionary definition and meaning for word foil
Foil as a verb, sounds like 'Spoil'. Hence: Spoil, Thwart, Queer, Frustrate
foil(verb)-- sounds like foul -- holland made fouls to "defeat" spain but they were not "frustrated" at all
foil=For(f)+OIL. Afghanistan foiled US on the issue of OIL, For oil.