I agree with you jabird, this is a thread about "What makes a hub airport?"
The true name for a hub is an airline hub. An airline hub is an airport that an airline uses as a transfer point to get passengers to their intended destination.
An airline like British Airways have three London hubs; Heathrow, Gatwick and London City. The last one is a BA Cityflyer hub. It is possible at ba.com to get tickets from Edinburgh to Zurich with transfer at LCY, and it is no surprise that transfering at LCY gives the shortest travel time between the two cities flying with BA. One thing wonders me though, why is it not possible to bye a ticket on ba.com from let us say New York to Copenhagen with transfer at London City?
It not only the legacy carriers that have hubs, even some of the low-cost carriers are hub carriers. Low-cost carriers like the two largest European, Ryanair and easyJet, have only bases and no hubs (they only sell point to point ticket with no transfer). Then there are carriers that have low costs but still offers transfer tickets, and examples of this are Air Berlin and Norwegian Air Shuttle.