#propeller__propellor  a mechanical device that rotates to push against air or water
  supertype:  mechanical_device  mechanism consisting of a device that works on mechanical principles
  subtype:  airplane_propeller  screw_propeller  variable-pitch_propeller
  part:  blade.rotating_mechanism__vane  flat surface that rotates and pushes against air or water
  part:  hub  the central part of a car wheel (or fan or propeller etc) through which the shaft or axle passes

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