Estoppel

n. impediment which prevents a party from denying an action which they have committed (Law)

Estoppel is a legal doctrine recognised both at common law and in equity in various forms. It is meant to complement the requirement of consideration in contract law. In general it protects a party who would suffer detriment if: The defendant has done or said something to induce an expectation The plaintiff relied (reasonably) on the expectation......and would suffer detriment if that expectation were false.
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Noun
1. a rule of evidence whereby a person is barred from denying the truth of a fact that has already been settled
(hypernym) rule of evidence

n. estoppel, impediment which prevents a party from denying an action which they have committed (Law)

(n.)
The agency by which the law excludes evidence to dispute certain admissions, which the policy of the law treats as indisputable.
  

(n.)
A stop; an obstruction or bar to one's alleging or denying a fact contrary to his own previous action, allegation, or denial; an admission, by words or conduct, which induces another to purchase rights, against which the party making such admission can not take a position inconsistent with the admission.