The term "Full Stack" outside of Pancakes is reference to all things required for serving internet enabled technology including websites, ecommerce systems, web hosted business systems, or  government systems.  

Full Stack includes reference to the power, hardware, networking,  hosting, security, database systems and front and back ends of sites and services, as as well as the sites themselves.  

It's a very, very  all inclusive phrase that can be applied to systems that are NOT accessible from the internet, too. 

You can, in fact, host and serve "web based software systems" on private networks. Many people do not realize that, just like many have forgotten the unadulterated beauty of a full stack of lusciously drenched and drippingly gorgeous pancakes too!