atomic clock

American  

noun

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

---

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

---

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.

---

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.

---

Etymology

Origin of atomic clock

First recorded in 1935–40

Example Sentences

Infleqtion doesn’t claim to be a quantum-computing pure play: One of its most commercially robust products, according to Kinsella, is an atomic clock called Tiqker.

From Barron's • Feb. 17, 2026

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

As that lighthouselike beam sweeps past Earth, radio telescopes register pulses as regular as an atomic clock.

From Science Magazine • Dec. 13, 2023

Scandium, an element used in aerospace components and sports equipment, enables an accuracy of one second in 300 billion years, or roughly a thousand times more precision than the current standard atomic clock.

From Science Daily • Nov. 3, 2023

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