1. (noun)foil a piece of thin and flexible sheetmetal "the photographic film was wrapped in foil"
2. (noun)foil, enhancer anything that serves by contrast to callattention to another thing's good qualities "pretty girls like plain friends as foils"
3. (noun)hydrofoil, foil a device consisting of a flat or curved piece (as a metal plate) so that its surface reacts to the water it is passing through "the fins of a fish act as hydrofoils"
6. (verb)foil enhance by contrast "In this picture, the figures are foiled against the background"
7. (verb)thwart, queer, spoil, scotch, foil, cross, frustrate, baffle, bilk hinder or prevent (the efforts, plans, or desires) of "What ultimately frustrated every challenger was Ruth's amazing September surge"; "foil your opponent"
8. (verb)foil cover or back with foil "foil mirrors"
4. (noun)foil a leaf or very thin sheet of metal; as, brass foil; tin foil; goldfoil
5. (noun)foil a thin leaf of sheet copper silvered and burnished, and afterwards coated with transparent colors mixed with isinglass; -- employed by jewelers to give color or brilliancy to pastes and inferior stones
6. (noun)foil anything that serves by contrast of color or quality to adorn or set off another thing to advantage
7. (noun)foil a thin coat of tin, with quicksilver, laid on the back of a looking-glass, to causereflection
8. (noun)foil the space between the cusps in Gothic architecture; a rounded or leaflike ornament, in windows, niches, etc. A group of foils is called trefoil, quatrefoil, quinquefoil, etc., according to the number of arcs of which it is composed