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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
Bradley Iger, Ars Technica, 2 Dec. 2023
In the Aston Martin layout, there’s a media display in the center, surrounded by the speedometer and tachometer, and outlined in the brand’s distinctive green.
—Richard Lawler, The Verge, 20 Dec. 2023
Among other things, the Trieste’s tachometer, which measured how fast the submarine was descending, broke before the mission even began.
—Gary Robbins, San Diego Union-Tribune, 29 Nov. 2023
Where the Miura has a simple, low dashboard showcasing a giant speedometer on the left, matching tachometer on the right, and ancillary gauges standing proud off to the side, the Countach jams everything into a traditional cluster behind the wheel.
—Tim Stevens, Robb Report, 4 May 2023
See all Example Sentences for tachometer 
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'tachometer.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
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Cite this Entry
“Tachometer.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/tachometer. Accessed 30 Jun. 2024.
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tachometer
noun
from Greek tachos "speed" and English meter "an instrument for measuring"
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