spark plug

US /ˈspɑːrk ˌplʌɡ/
UK /ˈspɑːrk ˌplʌɡ/
"spark plug" picture
1.

a device for firing the explosive mixture in an internal combustion engine

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The mechanic replaced the faulty spark plug.
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A worn-out spark plug can cause engine misfires.
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ignition plug
2.

a person or thing that is a catalyst for a development or event

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Her innovative idea was the spark plug for the entire project.
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He acted as the spark plug, motivating the team to achieve their goals.
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catalystimpetusstimulusinitiatordriver
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plugplug inplug intosparkplug and playplug awaypull the plug