spark plug—
1. a device that ignites the fuel mixture in an internal-combustion engine:
- Although you can’t see the spark plugs, you can see the spark plug wires that are attached to each of them.
2. a person who is the driving force behind an activity or undertaking:
- It is thrilling to have someone who is a great role model for the young, who is a spark-plug for the team.
sparking plug — = spark plug 1:
- Pull off the cap of the sparking plug so that the engine cannot be started inadvertently.