the central part of a car wheel (or fan or propeller etc) through which the shaft or axle passes
a center of activity or interest or commerce or transportation; a focal point around which events revolve; "the playground is the hub of parental supervision"; "the airport is the economic hub of the area"
a splendid assemblage (especially of famous people)
(astronomy) a collection of star systems; any of the billions of systems each having many stars and nebulae and dust; "`extragalactic nebula' is a former name for `galaxy'"