The Collaborative International Dictionary of English v.0.48:

Hub \Hub\ (h[u^]b), n. [See 1st Hob.]
   1. The central part, usually cylindrical, of a wheel; the
      nave. See Illust. of Axle box.
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   2. The hilt of a weapon. --Halliwell.
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   3. A rough protuberance or projecting obstruction; as, a hub
      in the road. [U.S.] See Hubby.
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   4. A goal or mark at which quoits, etc., are cast.
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   5. (Diesinking) A hardened, engraved steel punch for
      impressing a device upon a die, used in coining, etc.
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   6. A screw hob. See Hob, 3.
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   7. A block for scotching a wheel.
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   8. The central location within which activities tend to
      concentrate, or from which activities radiate outward; a
      focus of activity.
      [PJC]

   9. Hence: (Aeronautics) A large airport used as a central
      transfer station for an airline, permitting economic air
      transportation between remote locations by directing
      travellers through the hub, often changing planes at the
      hub, and thus keeping the seat occupancy rate on the
      airplanes high. The hub together with the feeder lines
      from remote locations constitute the so-called

   hub and spoke system of commercial air passenger
      transportation. A commercial airline may have more than
      one such hub.
      [PJC]

   10. The city of Boston, Massachusetts referred to locally by
       the nickname The Hub.
       [PJC]

   Hub plank (Highway Bridges), a horizontal guard plank along
      a truss at the height of a wagon-wheel hub.

   Up to the hub, as far as possible in embarrassment or
      difficulty, or in business, like a wheel sunk in mire;
      deeply involved. [Colloq.]
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