plebiscite

Short definition from Wiktionary

Noun

1. 1
   A direct popular vote on an issue of public importance, such as an amendment to the constitution, a change in the sovereignty of the nation, or some government policy.
2. 2
   An expression of the public's views on an issue, whether legally binding or not.
3. 3
   Synonym of plebiscitum (“a law enacted by the common people, under the superintendence of a tribune or some subordinate plebeian magistrate, without the intervention of the senate”).