Because everyone is demanding, rightly, that one define one’s concept of free will before discussing it, I will offer one here, subject, of course, to modification if it proves incoherent or useless:
A person makes a decision. Now rewind the tape leading up to the moment of that decision. Everything remains exactly the same as before: the history of the universe, the person’s entire life, experiences, and body, and so on. If on the rewind the person makes a decision different from the one before, then that person had free will.
Because I’m a physical determinist, I don’t think that making a different decision is possible, and so free will is impossible. But at least the definition has the merit of being specific. And it’s sort of intuitive: put a guy at the ice cream counter, and if he decides to order butter pecan instead of chocolate, well, that’s a free choice.