What is the meaning of foil?

noun

• A piece of thin and flexible sheet metal.
  • usage: "the photographic film was wrapped in foil"
• Anything that serves by contrast to call attention to another thing's good qualities.
  • usage: "pretty girls like plain friends as foils"
  • synonyms: enhancer
• 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.
  • usage: "the fins of a fish act as hydrofoils"
  • synonyms: hydrofoil
• Picture consisting of a positive photograph or drawing on a transparent base; viewed with a projector.
  • synonyms: transparency
• A light slender flexible sword tipped by a button.

verb

• Enhance by contrast.
  • usage: "In this picture, the figures are foiled against the background"
• Hinder or prevent (the efforts, plans, or desires) of.
  • usage: "What ultimately frustrated every challenger was Ruth's amazing September surge"; "foil your opponent"
  • synonyms: thwart, queer, spoil, scotch, cross, frustrate, baffle, bilk
• Cover or back with foil.
  • usage: "foil mirrors"