1 : the central and most active part or place
the hub of the city
The island is a major tourist hub. [=a place where many tourists go]
She was at the hub of all the activity.
2 : the airport or the city through which an airline sends most of its flights
All of the airline's coast-to-coast flights pass through its hub.
3 : the center of a wheel, propeller, fan, etc.
The spokes attach to the hub of the wheel.