sparking plug

Definition

Cars & Driving

  • noun a device screwed into the cylinder head of spark ignition engines (one sparking plug per cylinder) which initiates fuel combustion by an electric spark arcing from the centre electrode to the side electrode; typically consisting of a steel shell with a hexagon and a thread with the welded-on side electrode, a ceramic insulator and the centre electrode
http://www.dictionarycentral.com/definition/sparking-plug.html