frustrate, thwart, foil, baffle, balk mean to check or defeat another's plan or block achievement of a goal. frustrate implies making vain or ineffectual all efforts however vigorous or persistent.

FOIL definition: to prevent the success of; frustrate; balk. See examples of foil used in a sentence.

FOIL definition: 1. a very thin sheet of metal, especially used to wrap food in to keep it fresh: 2. a piece of a…. Learn more.

Look up foil in Wiktionary, the free dictionary.

One that stands in contrast to and emphasizes the distinctive characteristics of another: "I am resolved my husband shall not be a rival, but a foil to me" (Charlotte Brontë).

Dec 24, 2025 · foil (countable and uncountable, plural foils) A very thin sheet of metal or plastic. (chiefly uncountable) Thin aluminium / aluminum (or, formerly, tin) used for wrapping food. A …

If you refer to one thing or person as a foil for another, you approve of the fact that they contrast with each other and go well together, often in a way that makes the second thing or person …

FOIL meaning: 1 : to prevent (someone) from doing something or achieving a goal defeat often used as (be) foiled; 2 : to prevent (something) from happening or being successful

As a verb, if you foil someone's plans or attempts to do something, you cause them to fail. Your brother will be really mad if you foil his plans to hide his mediocre report card from your parents.

Aluminium foil (or aluminum foil in American English; also called tinfoil) is aluminium prepared in thin metal leaves. The foil is pliable and can be readily bent or wrapped around objects.