Many people would get offended if you start asking questions like this. So, is it a stupid question? Possibly. And possibly not. If they can give you a clear definition and show that everybody uses this definition, then it is fine. If not, you have a (political) problem to deal with.
Semantic integration is what integration is about first and foremost, with technical integration coming in on second place. You need first to ensure that "customer" in one business system means the same thing as "customer" in another business system if you are to integrate them, not just make sure that you map attributes in the correct way. And to be able to ensure that, you need a common definition on enterprise level of the customer concept (which might not be exactly the same as in any of the systems to be integrated).