/ ɪgˈnɪʃn; NAmE / noun
1.
[ C , usually sing. ] the electrical system of a vehicle that makes the fuel begin to burn to start the engine; the place in a vehicle where you start this system :
to turn the ignition on / off
to put the key in the ignition
—picture at car
2.
[ U ] ( technical ) the action of starting to burn or of making sth burn :
The flames spread to all parts of the house within minutes of ignition.
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WORD ORIGIN
early 17th cent. (denoting the heating of a substance to the point of combustion or chemical change): from medieval Latin ignitio(n-) , from the verb ignire set on fire, from ignis fire.