I think he was using that word not as a technical term, but as a way of saying "even faster/sharper than exponential". I.e., hyper- (the prefix meaning above) + exponential.

Certainly O(N^2) is not at the top of the food chain -- for example, it is beaten by O(2^N) or O(N!) or O(N^N). All of these could, colloquially, be referred to as "hyper"exponential.

Imagine a hockey stick graph (exponential). Now imagine that hockey stick graphed on a logarithmic scale -- the logarithms more or less cancel out the exponentiation if done right, making the graph appear to be linear even though the data is exponential. Now, imagine data that, even when graphed on a logarithmic scale, still looks like a hockey stick. That is hyperexponential.

And I think I just proved Sam's point -- that it is hard to visualize/grok.