noun Thin aluminium/aluminum (or, formerly, tin) used for wrapping food.
wrap the sandwich up in foil
noun A thin layer of metal put between a jewel and its setting to make it seem more brilliant.
noun 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.
noun Anything that acts by contrast to emphasise the characteristics of something.
noun A very thin sword with a blunted (or foiled) tip.
noun A thin, transparent plastic material on which marks are made and projected for the purposes of presentation. See transparency.