Estoppel is an equitable doctrine, a bar that prevents one from asserting a claim or right that contradicts what one has said or done before, or what has been legally established as true. Estoppel may be used as a bar to the re-litigation of issues or as an affirmative defense.
For estoppel in contract law, promissory estoppel is often applied where there is a promise or an agreement made without consideration.
[Last updated in September of 2022 by the Wex Definitions Team]