Copilot Key Definitions currently support a defined set of objects: Company, Call To Action, Task, Success Plans, Activity Timeline, and User Objects.
Scorecards are not on that list (although Copilot doesn't appear to know that - unsurprising):

What is surprising, however, is that I’ve been told to submit this as an “enhancement request/idea” in the community.
How is this not already on the roadmap for Key Definitions!?
Key Definitions need to work fully with Scorecard data—not in a limited "basic queries only" capacity, but in a way that reflects how Scorecards are actually used by customers day to day.
For that matter, Key Definitions should work with every major Gainsight Standard object, (as well as Custom Objects and Data Designer objects, if those are also not on the roadmap)
Key Definitions exist to give Copilot the business context it needs to interpret user questions accurately—translating your organization's data language and logic into consistent, relevant responses. This should include all major areas where we need to provide said context.