accelerator
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$ \mathrm{accelerator} /əkˈseləreɪtə(r)/
1 (also gas pedal) the pedal in a car or other vehicle that you press with your foot to control the speed of the engine
She put her foot on the accelerator and we sped through the traffic lights.
verb + accelerator
accelerator + noun
2 (physics) a machine for making elementary particles move at high speeds