NOUN (2)

1. the central part of a car wheel (or fan or propeller etc) through which the shaft or axle passes;

2. a center of activity or interest or commerce or transportation; a focal point around which events revolve;
- Example: "the playground is the hub of parental supervision"
- Example: "the airport is the economic hub of the area"

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.
      [1913 Webster]

   2. The hilt of a weapon. --Halliwell.
      [1913 Webster]

   3. A rough protuberance or projecting obstruction; as, a hub
      in the road. [U.S.] See Hubby.
      [1913 Webster]

   4. A goal or mark at which quoits, etc., are cast.
      [1913 Webster]

   5. (Diesinking) A hardened, engraved steel punch for
      impressing a device upon a die, used in coining, etc.
      [1913 Webster]

   6. A screw hob. See Hob, 3.
      [1913 Webster]

   7. A block for scotching a wheel.
      [1913 Webster]

   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.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

nave \nave\ (n[=a]v), n. [AS. nafu; akin to D. naaf, G. nabe,
   OHG. naba, Icel. n["o]f, Dan. nav, Sw. naf, Skr. n[=a]bhi
   nave and navel: cf. L. umbo boss of a shield. [root]260. Cf.
   Navel.]
   1. The block in the center of a wheel, from which the spokes
      radiate, and through which the axle passes; -- called also
      hub or hob.
      [1913 Webster]

   2. The navel. [Obs.] --hak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hub
    n 1: the central part of a car wheel (or fan or propeller etc)
         through which the shaft or axle passes
    2: 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"

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "hub":
   approach, arbor, asymptote, axis, axle, axle bar, axle shaft,
   axle spindle, axle-tree, bottleneck, center, center of action,
   center of gravity, centroid, centrum, chimney, chimney corner,
   collision course, concentralization, concentration, concourse,
   concurrence, confluence, conflux, congress, convergence,
   converging, core, crossing, dead center, distaff, epicenter,
   fender, fire screen, fireboard, fireguard, fireplace, fireside,
   flue, focal point, focalization, focus, fulcrum, funnel, gimbal,
   gudgeon, heart, hearth, hearthstone, hinge, hingle, hob, ingle,
   inglenook, ingleside, kernel, mandrel, marrow, medulla, meeting,
   metacenter, middle, mutual approach, narrowing gap, nave, navel,
   nerve, nub, nucleus, oarlock, omphalos, pin, pintle, pith, pivot,
   pole, radiant, radius, rowlock, seat, smokehole, spindle, spokes,
   storm center, swivel, tangent, trunnion, umbilicus



The Free On-line Dictionary of Computing (30 December 2018):

hub
hubs

    (By analogy with the hub of a wheel) A device
   connected to several other devices.

   In ARCnet, a hub is used to connect several computers
   together.  In a message handling service, a number of local
   computers might exchange messages solely with a hub computer.
   The hub would be responsible for exchanging messages with
   other hubs and non-local computers.

   (1995-01-16)