Smith directed Willis on 2009 comedy Cop Out, but claimed soon after the film's release that he had a hard time working with him on set and labelled the former Die Hard star a "f**king d**k".
Willis tried to distance himself from the feud, insisting there was no bad blood between the pair, but Smith has fuelled the argument once more with a rant on Twitter.com.
He writes, "Who am I talking about when I write this: 'He turned out to be the unhappiest, most bitter and meanest emo-b**ch I ever met at any job I've held. And mind you, I worked at Domino's.'"
When a fan tweeted back, "Bruce Willis", Smith replied, "Took you all of 31 secs! WINNER-WINNER!"