#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 of:  #reciprocating_engine
  part:  #piston_ring  seal consisting of a split metal ring that seals the gap between a piston and the cylinder wall
  part:  #piston_rod  connecting rod that moves or is moved by a piston

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