The Kantian definition of talent in the context of imperfect duties is that these are abilities that can help others. The reason for this is that the justification for why we must develop our talents follows from a human limitation and the Categorical Imperative.
Specifically, as human beings,
(1) we need help at different points in our lives
The Categorical Imperative means that we need maxims that can be universal.
But this means that we somehow need the Categorical Imperative to include requiring rational creatures to provide us with aid. So we universalize that and it applies back upon ourselves. Thus, the talents that matter are those that can help people.
From this, however, it does not follow that juggling is excluded. Because we have wide latitude in selecting our talents that we develop. And there are many different forms of assistance we may need throughout our lives. What seems like it would be excluded is an ability that is improved which could never help others or an improvement in level in ability that one could not conceive of helping others. So then maybe playing video games is not a talent under this definition. But again, we are not required to spend every waking moment improving our talents.