It's called a "diablo"...see the link.
Linda C

Here is a link that might be useful: toy

You're welcome!
I don't mean to reprimand.....well maybe I do a bit....
But when someone goes to the trouble to look up and post a link in answer to your question, it's polite to at least sign on and post a thank you....

Hi lindac,

Truly, very sorry for not yet responding and very appreciative of your response.

A little background, but no excuse on my part.
The park where I saw the guy using the diabolo was in Tokyo. I was there for 3 weeks on business and just returned to the US East Coast last weekend. I'm still plowing through the tons of email that we all get these days (while enjoying the symptoms of jet lag). :-)

I'm planning on buying a diabolo because it looks very interesting.

Thank you,
Kevin