A constitutional convention is now a gathering for the purpose of writing a new constitution

Constitution

A constitution is a set of fundamental principles or established precedents according to which a state or other organization is governed. These rules together make up, i.e. constitute, what the entity is...

 or revising an existing constitution. A general constitutional convention is called to create the first constitution of a political unit or to entirely replace an existing constitution. An unlimited constitutional convention is called to revise an existing constitution to the extent that it deems to be proper, whereas a limited constitutional convention is restricted to revising only the areas of the current constitution named in the convention's call, the legal mandate establishing the convention.
Examples of constitutional conventions include:

• United States: Annapolis Convention (1786)
  Annapolis Convention (1786)
  The Annapolis Convention was a meeting in 1786 at Annapolis, Maryland, of 12 delegates from five states that unanimously called for a constitutional convention. The formal title of the meeting was a Meeting of Commissioners to Remedy Defects of the Federal Government...
  
  , which proposed what became the Philadelphia Convention
  Philadelphia Convention
  The Constitutional Convention took place from May 14 to September 17, 1787, in Philadelphia, Pennsylvania, to address problems in governing the United States of America, which had been operating under the Articles of Confederation following independence from...
  
   (1787) – Drafted the United States Constitution
  United States Constitution
  The Constitution of the United States is the supreme law of the United States of America. It is the framework for the organization of the United States government and for the relationship of the federal government with the states, citizens, and all people within the United States.The first three...
  
   for ratification by the states.