How Big is "Giant"?

Several times I've mentioned my giant black Maine Coon/Norwegian Forest Cat mix. When I say he's big, I mean it!

How big, exactly? Here's a photo that gives a really good example of his size. It's a couple years old, and taken before he was done growing, so he's actually even bigger now. But it's still the best example I have.

Please keep in mind that the other two cats are your perfectly average-sized 10lb male cats.