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A tachometer is literally a "speed-measurer", since the Greek root tach- means "speed". This is clear in the names of the tachyon, a particle of matter that travels faster than the speed of light (if it actually exists, it's so fast that it's impossible to see with any instrument), and tachycardia, a medical condition in which the heart races uncontrollably. Since the speed that an auto tachometer measures is speed of rotation of the crankshaft, the numbers it reports are revolutions per minute, or rpm's.
Examples of tachometer in a Sentence
Utkarsh Sood
june 13, New Atlas, 13 June 2026
The driver faces a simple layout centered around the steering wheel, pedals, tachometer and shifter, with little or wasted space.
—Josh Max, Forbes.com, 8 June 2026
Once the roads open and the Miura’s tachometer sweeps past 4,000 rpm, however, your ears are nourished by a cultured snarl that builds to a hammering roar.
—Tim Pitt, Robb Report, 18 May 2026
The latter offers a layout featuring a prominent round tachometer in the center of the cluster flanked by customizable displays for the engine’s effort, suspension settings and other monitoring.
—James Raia, Mercury News, 2 June 2025
See All Example Sentences for tachometer
Cite this Entry
“Tachometer.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/tachometer. Accessed 22 Jun. 2026.
Copy CitationKids Definition
tachometer
noun
from Greek tachos "speed" and English meter "an instrument for measuring"
