atomic clock

American  

noun

1. an extremely accurate electronic clock regulated by the resonance frequency of atoms or molecules of certain substances, as cesium.

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atomic clock British  

noun

1. an extremely accurate clock in which an electrical oscillator is controlled by the natural vibrations of an atomic or molecular system such as caesium or ammonia

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atomic clock Scientific  

1. An extremely precise clock whose rate is controlled by a periodic process (such as vibration, or the absorption or emission of electromagnetic radiation) that occurs at a steady rate in atoms or molecules. The standard atomic clock is based on the vibrations of cesium atoms and is so accurate that it would gain or lose less than one second in three million years. Atomic clocks are used to help track satellites, run navigation systems, and study movements of the Earth's crust.

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atomic clock Cultural  

1. The most accurate clock available. Time is measured by the movement of electrons in cesium atoms. The standard second is now defined by measurements on an atomic clock.

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Etymology

Origin of atomic clock

First recorded in 1935–40

Example Sentences

It offers products such as the Tiqker atomic clock.

From Barron's • Feb. 17, 2026

An atomic clock placed on the surface of Mars would function normally.

From Science Daily • Dec. 30, 2025

Even the atomic clock at the National Institute of Standards and Technology, the federal agency that oversees the Internet Time Service, lost five-millionths of a second because of the electrical outages.

From The Wall Street Journal • Dec. 25, 2025

In 1955, the NPL invented the first atomic clock of the sort that is used today, based on the frequency of radiation from an atom of the element caesium.

From BBC • Mar. 2, 2025

What we want is the middle line, which tells you the exact Mountain Standard Time, as determined by a government-run atomic clock in Boulder, Colo.

From Big Dummy's Guide to the Internet by Electronic Frontier Foundation