Meaning of "if not" in "if not [some trait]"

Question

If I say:

You are well-established if not dominant in your field

am I saying that you're not dominant or that you are?

Answer 1

This is a reasonably common idiomatic expression.

You are saying that the person is well established, and might be dominant in their field.

It says that "If you are not dominiant, then you are well estabished." But since being dominant is stronger than being well established it is also true that if you are dominant then you are also well established. So the meaning is "you are well established, and you might be dominant"

You sometimes see this pattern with superlatives

You are an intelligent, if not the most intelligent, person in the school.