What is the meaning of Rootof in my CAS?

[Matt Jacques]

What does "Rootof" mean?

My CAS is saying RootOf, now this is clearly different than sqrt or cbrt, any ideas what it means?

 

[Integral]

What is CAS?
I would interpret rootof to be the square root.

 

[Zurtex]

I would interpret the root of f(x) to be the value of x such that f(x)=0

If that helps