From Longman Business Dictionaryconsensus ad idemconsensus ad i‧dem /kənˌsensəs æd ˈaɪdem, -ˈɪdem-ˈaɪdem/ noun [uncountable] LAW agreement between all the people or groups who make a contract on what they understand the contract to be about. Consensus ad idem must exist before a court can force any of the people or groups to obey the contract