"Empty promise" definition?

You may remember, as a child, turning to your parents to ask what a particular word means from time to time. So you don't have to be a professional linguist, like me, to do what a dictionary does, but even so... maybe you have heard phrases like "pyrrhic victory"? ...How many of you know what an "empty promise" is, yet just can't define it? (By the way, if anyone comes across a definition of it online or in whatever dictionary, I'd love to hear it.)

I'm going to have a go at outlining an "empty promise" right now...

When a person makes a promise to someone when that promise does not have as much value as the first person tries (consciously or not) to have the second person believe?

When a person makes a promise to someone where the promise is expected to be fulfilled as a result of something that should happen even though the person making the promise is less than confident about it (especially if the person making the promise has no control over what would fulfill it, or contribute to fulfill it)?