foil definition

1. a piece of thin and flexible sheet metal
• examples: the photographic film was wrapped in foil
2. anything that serves by contrast to call attention to another thing's good qualities
• examples: pretty girls like plain friends as foils
3. picture consisting of a positive photograph or drawing on a transparent base; viewed with a projector
4. a light slender flexible sword tipped by a button
5. enhance by contrast
• examples: In this picture, the figures are foiled against the background
6. cover or back with foil
• examples: foil mirrors