Technical Definition of Badass: Given a representative task in the domain, a badass performs in a superior way, more reliably.
— Kathy Sierra, Badass: Making Users Awesome

Sierra continues:

Experts are what they do not just what they know.

It's what they do with what they know.

And it's their ability to do it again and again and again.

Expert/badass performance is both superior and more consistent than the performance of those who are knowledgeable and experienced but not producing expert results.

Experts make better choices than others.