The term “default-free routing” relates to network routing where there is no default route used. It’s a convention to set a default route in networking such that packets are always forwarded ‘somewhere’. Typically, that somewhere is the Internet. Because the Internet has hundreds of thousands of routes its not possible to load those routes into Enterprise network routers.
Unless you use proxy servers to access the Internet, in which case your web browsers can be configured to explicitly the proxy servers for all Internet requests and your corporate network will be configured with “default-free routing”.
Default-free routing has many advantages, the most well known is when scanning malware outbreaks occur, the traffic from the scan has almost nowhere to go.
Typically, Internet backbone routers are also “default-free routing” since they contain all the routes of the Internet in their RIB and the use of the a default route makes no sense.