What exactly is a mandate?

This quote from the Associated Press in an article entitled "Obama eyes use of executive orders" disturbs me because of the word 'mandate'.

"There's a lot that the president can do using his executive authority without waiting for congressional action, and I think we'll see the president do that," John Podesta, Obama's transition chief said. "I think that he feels like he has a real mandate for change. We need to get off the course that the Bush administration has set."

I told my wife on Sunday to watch out for the first day Executive Orders that Obama would sign, and also the ones that he would rescind of Bush's---this is no surprise.

However, let's focus on that word 'mandate'---what exactly is a mandate?