Floating routes are somtetime static routes with another administrativ distance. These routes disapear, when dynamic routes are no longer valid. This could be a technique to prove certain rechability for networks. Floating means, that they are there but you can’t see them until they get valid.
If there is for example a dynamic default route is learned from EIGRP with Administrativ distance 90 or for external EIGRP routes with AD 170, then you could place a static route with „ip route 0.0.0.0 0.0.0.0 s0/0 171“, so that it will apear in the routing table, when the AD 90 or 170 default route does not longer exists.
That’s called a floating route.