foil

1. A very thin sheet of metal.
2. Thin aluminium/aluminum (or, formerly, tin) used for wrapping food.

   wrap the sandwich up in foil

3. A thin layer of metal put between a jewel and its setting to make it seem more brilliant.
4. (authorship) In literature, theatre/theater, etc., a character who helps emphasize the traits of the main character and who usually acts as an opponent or antagonist.
5. Anything that acts by contrast to emphasise the characteristics of something.
6. A very thin sword with a blunted (or foiled) tip
7. A thin, transparent plastic material on which marks are made and projected for the purposes of presentation. See transparency.
8. A stylized flower or leaf.
9. A hydrofoil.
10. An aerofoil/airfoil.

verb

To cover or wrap with foil.

1. Failure when on the point of attainment; defeat; frustration; miscarriage.
2. One of the incorrect answers presented in a multiple-choice test.

1. To prevent (something) from being accomplished.

   I was foiled by my superior

2. To prevent (someone) from accomplishing something.

   They foiled my plans.

3. To blunt; to dull; to spoil.

   to foil the scent in hunting

4. To tread underfoot; to trample.

noun

The track of an animal.

verb

To expand a product of two or more algebraic expressions, typically binomials.

verb

To defile; to soil.