Estoppel
WordNet
noun
(1) A rule of evidence whereby a person is barred from denying the truth of a fact that has already been settled
WiktionaryText
Noun
- a legal principle in the law of equity that prevents a party from asserting otherwise valid legal rights against another party because conduct by the first party makes, or circumstances to which the first party has knowingly contributed, make it unjust for those rights to be asserted.