- an electrical device threaded into the cylinder of an internal-combustion engine to ignite the fuel mixture by producing timed sparks between electrodes
- Informal a person or thing that inspires, activates, or advances something
- A device inserted in the head of an internal-combustion engine cylinder that ignites the fuel mixture by means of an electric spark.
- Informal One who gives life or energy to an endeavor.
B. ceramic insulation
C. center electrode
E. ground electrode