That definition has to include the idea of approximation. Part of the deep attraction of music making is that you can always get closer and closer to being better able to express yourself musically. If that's not part of your practice of music, burnout becomes probable.
What's so recharging about music making is that the more you do it, the more it helps you understand what it is you're trying to express. That other great American poet, T. S. Eliot, in his usual grim way, gets at this issue here:
. . . one has only learnt to get the better of words
For the thing one no longer has to say, or the way in which
One is no longer disposed to say it. And so each venture
Is a new beginning, a raid on the inarticulate . . .
It's like blogging. The more I try to say what I think I mean, the better I understand the thoughts beneath the language trying to find a way out. And the same goes for music making, with each approximation getting closer and closer to pure expression, but rarely, if ever, getting there.