Like any legal document, the parties are not free to change the meaning of it's terms once the document is enacted, except in cases where the document itself provides procedures for doing so. In the case of the Constitution, that's called the amendment process. I'm aware of no amendment that changes the definition of natural born citizen. Yes an amendment does declare that all persons born here are citizens, but it doesn't not define them as natural born citizens. So, whatever the term meant when the Constitution was written and ratified, it means the same today.
Wrong way to look at it.
Natural Born Citizen has always meant Citizen at Birth.
However, when Common Law controlled this issue, both terms still meant the same thing.
The Founders meant that you had to be a Citizen at Birth, and at the time they wrote and ratified those words, they also gave Congress the power to define Citizenship clearly.