Capacitance afterfiring

The continuation of the spark across the gap in a shielded spark plug after the air/fuel mixture in the cylinder is ignited. Afterfiring is caused by the return of electrical energy stored in the capacitance of the shielded ignition leads. Capacitance afterfiring is eliminated by the use of a resistor in the spark plug.

Aviation Maintenance Technician Handbook — Powerplant, p. G-5