ignition

noun5

1. •
   The act of igniting.
2. •
   A system for activating combustion in a combustion engine.
3. •
   Receptacle for a key used to start the engine in a vehicle.

   • Put the key in the ignition and turn in right.
4. •
   The initiation of combustion.
5. •
   The phenomenon of a thermonuclear fusion reaction becoming self-sustaining and no longer requiring external heating.