foil

Short definition from Wiktionary

Noun

1. 1
   A very thin sheet of metal.
2. 2
   Thin aluminium/aluminum (or, formerly, tin) used for wrapping food.
3. 3
   A thin layer of metal put between a jewel and its setting to make it seem more brilliant.
4. 4
   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, but can also serve as the sidekick of the protagonist.
5. 5
   Anything that acts by contrast to emphasise the characteristics of something.
6. 6
   A very thin sword with a blunted (or foiled) tip
7. 7
   A thin, transparent plastic material on which marks are made and projected for the purposes of presentation. See transparency.
8. 8
   A premium trading card with a glossy finish.
9. 9
   A stylized flower or leaf.
10. 10
    Clipping of hydrofoil.
11. 11
    Clipping of aerofoil/airfoil.
12. 12
    Failure when on the point of attainment; defeat; frustration; miscarriage.
13. 13
    One of the incorrect answers presented in a multiple-choice test.
14. 14
    The track of an animal.
15. 15
    A small arc in the tracery of a window, etc.

Verb

1. 1
   To cover or wrap with foil.
2. 2
   Clipping of hydrofoil.
3. 3
   To prevent (something) from being accomplished.
4. 4
   To prevent (someone) from accomplishing something.
5. 5
   To blunt; to dull; to spoil.
6. 6
   To tread underfoot; to trample.
7. 7
   To expand a product of two or more algebraic expressions, typically binomials.
8. 8
   To defile; to soil.
9. 9
   To apply the FOIL algorithm to.

Proper noun

1. 1
   An acronym for the algorithm for multiplying two binomials.