"Free will is essentially an oxymoron — we would not consider it 'will' if it were completely random and we would not consider it 'free' if it were entirely determined," Brembs said. In other words, nobody would ascribe responsibility to one's actions if they were entirely the result of random coincidence. On the other hand, if one's actions were completely determined by outside factors such that no alternative existed, no one would hold that person responsible for them."

[From the article 'Study hints that fruit flies have free will' by Charles Q. Choi]

So what is free will? Can an action be partially determined?