1. a legal bar to alleging or denying a fact because of one's own previous actions or words to the contrary

2. a bar to the use of contradictory words or acts in asserting a claim or right against another especially equitable estoppel in this entry — compare waiver — equitable estoppel an estoppel that prevents a person from adopting a new position that contradicts a previous position maintained by words, silence, or actions when allowing the new position to be adopted would unfairly harm another person who has relied on the previous position to his or her loss — called also estoppel in pais Note: Traditionally equitable estoppel required that the original position was a misrepresentation which was being denied in the new position. Some jurisdictions retain the requirement of misrepresentation.

3. an estoppel precluding a person from denying the truth of any matter that he or she asserted in a deed especially regarding his or her title to the property — compare after-acquired title at title

4. an estoppel preventing a person from making an assertion to another's disadvantage when the person previously had the opportunity and duty to speak but failed to do so

5. equitable estoppel in this entry

6. an estoppel in patent law barring an applicant who has acquiesced in the rejection of a broad claim in the application for a patent from later asserting that a claim deliberately more restricted is equivalent to the original claim — called also prosecution history estoppel

7. an estoppel that prevents a promisor from denying the existence of a promise when the promisee reasonably and foreseeably relies on the promise and to his or her loss acts or fails to act and suffers an injustice that can only be avoided by enforcement of the promise

8. file wrapper estoppel in this entry

9. an equitable estoppel that does not require misrepresentation by one party nor reliance or ignorance by the other party

10. a bar to the relitigation of issues — collateral estoppel estoppel by judgment barring the relitigation of issues litigated by the same parties on a different cause of action broadly estoppel by judgment barring the relitigation of issues litigated by the same parties on a different or the same cause of action

11. estoppel by judgment barring the relitigation of issues litigated by the same parties on the same cause of action

12. a bar to the relitigation in a second action of issues already determined in a previous action especially collateral estoppel in this entry — called also estoppel by verdict, issue preclusion — see also former adjudication — compare merger sense 4, res judicata

13. the affirmative defense of estoppel

14. arising from the operation of estoppel
an entrapment by estoppel