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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
Viju Mathew, Robb Report, 29 Nov. 2025
With the air conditioning blasting and the revs low on the tachometer, the engine never seemed to charge the battery pack.
—Michael Teo Van Runkle, Forbes.com, 1 July 2025
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
The idea is to inform drivers when to shift the eight-speed transmission through pure audio feedback, without having to look at the tachometer.
—Karl Brauer, Forbes, 12 Mar. 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 Dec. 2025.
Copy CitationKids Definition
tachometer
noun
from Greek tachos "speed" and English meter "an instrument for measuring"
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