Constitutional convention (political meeting)

A constitutional convention is a gathering for the purpose of writing a new constitution or revising an existing constitution. 
Members of a constitutional convention (sometimes referred to as "delegates" to a constitutional convention) are often, though not necessarily or entirely, elected by popular vote. However, a wholly popularly-elected constitutional convention can also be referred to as a constituent assembly.
Examples.
National Conventions.
Examples of constitutional conventions to form or revise the constitution of a nation include:
Smaller Administrative Units.
Constitutional conventions have also been used by constituent states of federations — such as the individual states of the United States — to create, replace, or revise their own constitutions. Several U.S. states have held multiple conventions over the years to change their particular state's constitutions.