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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
James Raia, Mercury News, 2 June 2025
That means your maps, music, messages, speedometer, tachometer, and even tire pressure all live in one seamless interface.
—Paul Lamkin, Forbes.com, 16 May 2025
The instrument cluster features throwback green digits on the tachometer, accents mirrored on the Sport Chrono stopwatch (on that note, the automaker has created a high-quality chronograph exclusively offered for buyers of the 911 Spirit 70.
—Michael Harley, Forbes.com, 23 Apr. 2025
The engine rasps and rumbles right up to the tachometer’s 7,000-rpm redline—and beyond, in fact, since peak power arrives at 7,500 rpm.
—Michael Teo Van Runkle, Forbes.com, 23 Apr. 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 2 Jul. 2025.
Copy CitationKids Definition
tachometer
noun
from Greek tachos "speed" and English meter "an instrument for measuring"
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