It’s careless of me to say it’s a definition of intelligence, but I do think that property of being able to improve how you learn and how quickly you learn (especially in response to adversaries doing the same thing) is a clear indicator of intelligence and there’s a good argument that that’s why we developed intelligence. These aren’t my ideas either, I’m just parroting what I recently read in the book “What is Intelligence” by Blaise Aguera y Arcas.
I do like that meta observation though that not only do people get better at prediction through learning they can also get better at the rate at which they improve their predictions.