Cuban was initially supportive of Trump's presidential run when he first announced it, but Cuban has been lashing out at Trump lately over his lack of concrete policies.
"He had a really good chance to be different and really have a chance to change things, but he doesn't do the work. He's lazy," Cuban said.
Trump's campaign has been rolling out more policy proposals recently, but it still doesn't seem like he wants to talk with Cuban all that much.
"The problem with Mark, he's not smart enough to understand what we're doing," Trump said. "He's really not smart enough."