Talk:Rational variety

What does "dominated by a rational variety" mean?
The section on Unirationality begins as follows:

"A unirational variety V over a field K is one dominated by a rational variety, so that its function field K(V) lies in a pure transcendental field of finite type (which can be chosen to be of finite degree over K(V) if K is infinite)."

But there is no explanation or link that defines what "dominated by a rational variety" means.

So this is an example of extremely poor mathematical writing in Wikipedia.

In the sense that a chain is only as strong as its weakest link, and an article is only as clear as its unclearest statement.

I hope someone knowledgeable about the subject can fix this problem.