Definition from Nolo’s Plain-English Law Dictionary
A clause intended to keep a person from doing something or not doing something. In a will, a no-contest clause is intended to keep beneficiaries of the will from challenging its terms. Such clauses usually state that if a beneficiary challenges the will and loses, that beneficiary will receive nothing under the will. Under some states' laws, no-contest clauses are unenforceable. Also called in terrorem clause, noncontest clause, terrorem clause, anticontest clause, and forfeiture clause.