1. Metal:
* A thin sheet of metal, especially aluminum, used for wrapping food, etc. This is the most common meaning.
* *I wrapped the leftovers in aluminum foil.*
2. Character:
* A character in a story who contrasts with another character (usually the protagonist) in order to highlight the other character's traits.
* *The villain is a classic foil to the hero's goodness.*
3. Fencing:
* A fencing weapon consisting of a long, flexible blade and a guard.
* *The fencer skillfully parried the opponent's foil thrust.*
4. Verb:
* To prevent something from having an effect, or to make something less effective.
* *Her confidence was foiled by the interviewer's harsh questions.*
5. Verb:
* To line with foil.
* *They foiled the cake pan to prevent sticking.*
To figure out the correct meaning of "foil," you need to consider the context of the sentence or situation.