You're just defining intelligence as "undefined", which okay, now anything is anything. What is the point of that?

Indeed, there's quite a lot of work that's been done on what these terms mean. The fields of neuroscience and cognitive science have contributed a lot to the area, and obviously there are major areas of philosophy that discuss how we should frame the conversation or seek to answer questions.

We have more than enough, trivially, to say that human intelligence is distinct, so long as we take on basic assertions like "intelligence is related to brain structures" since we know a lot about brain structures.