Ma can be translated as "gap", "space", "pause" or "the space between two structural parts."
I told him I love the "gratuitous motion" in his films; instead of every movement being dictated by the story, sometimes people will just sit for a moment, or sigh, or gaze at a running stream, or do something extra, not to advance the story but only to give the sense of time and place and who they are.
"We have a word for that in Japanese," he said. "It's called 'ma.' Emptiness. It's there intentionally." He clapped his hands three or four times. "The time in between my clapping is 'ma.' If you just have non-stop action with no breathing space at all, it's just busyness."
I think that helps explain why Miyazaki's films are more absorbing than the frantic action in a lot of American animation. "The people who make the movies are scared of silence" he said, "so they want to paper and plaster it over," he said. "They're worried that the audience will get bored. But just because it's 80 percent intense all the time doesn't mean the kids are going to bless you with their concentration. What really matters is the underlying emotions--that you never let go of those."
See also: storytelling.