The founders did not define any of the plain language of the Constitution, except treason.
Do you not know what “shall not be infringed” means because they did not attach a glossary?
Natural born citizen was a commonly understood phrase until concerted efforts to undermine it in the second half of the 20th century.
Apparently not since a lot of effort went into writing laws that defined who was natural-born and who wasn't, starting in 1787 I believe.