Well, a parsec is a distance (why it's completely nonsensical for Han Solo to brag that the Millenium Falcon completed the whatever whatever in twelve parsecs -- unless one wants to argue that the whatever whatever is twelve parsecs long, and he's just having Luke on. I have trouble believing it from what I remember of context, though). So I'd guess that a megaparsec is a thousand of them . . .

It's a good thing that I got up at 6:30 this morning, or my neighbor's loud music at 7:15 on a Saturday might be really annoying.