spark plug
  火花塞
  Spark plug. In internal-combustion engines with electric ignition, a plug, screwed into the cylinder head, connected with the induction coil or magneto circuit on the outside, and used to produce a spark to ignite the fuel-air mixture in the engine.
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  spark plug
       n : electrical device that fits into the cylinder head of an
           internal-combustion engine and ignites the gas by means
           of an electric spark [syn: sparking plug, plug]