#piston__plunger  mechanical device that has a plunging or thrusting motion
  supertype:  mechanical_device  mechanism consisting of a device that works on mechanical principles
  part:  piston_ring  piston_rod
  part of:  reciprocating_engine__reciprocatingengine  an internal-combustion engine in which the crankshaft is turned by pistons moving up and down in cylinders

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