Foil is a synonym of wafer.
As nouns the difference between foil and wafer
is that
foil is a very thin sheet of metal or
foil can be failure when on the point of attainment; defeat; frustration; miscarriage or
foil can be (hunting) the track of an animal while
wafer is wafer.
As a verb foil
is to prevent (something) from being accomplished or
foil can be (mathematics) to multiply two binomials together or
foil can be (obsolete) to defile; to soil.