The phrase "speedometer needle" refers to the indicator on a car's dashboard that shows how fast the car is moving. It looks like a needle on a dial and moves as you accelerate or decelerate.
Sentences with «speedometer needle»
When you're getting set for a highway run, the red speedometer needle steadily climbs as you effortlessly merge with traffic. (driving.ca)
There were other minor cosmetic differences, including a larger speedometer needle which made it hard to figure out the exact speed. (allpar.com)