"Historic referendum" refers to a vote or decision made by the people of a country that has significant importance and impact on the nation's history. Full definition
No coming event on the global political and economic calendar — even the U.S. presidential election — is more consequential than Britain's historic referendum on its membership in the European Union. (fortune.com)
It comes it emerged George Osborne has already banked # 500,000 since being booted out of No11 after Britain's historic referendum result. (thesun.co.uk)
Historic referendum vote in favour of leaving EU raises questions over futures of David Cameron and Jeremy Corbyn (theguardian.com)