Meaning of spark plug

spark' plug"

Pronunciation: [key]
  1. a device designed to fit in each cylinder of a gasoline-powered internal-combustion engine and to produce the electric spark for igniting the mixture of gasoline and air.
  2. a person who leads, inspires, or animates a group.

spark•plug

Pronunciation: (spärk'plug"), [key]
— -plugged, -plug•ging.
  1. to lead, inspire, or animate something or someone.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.