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• laser
  laser

  noun

  a device that produces a nearly parallel, nearly monochromatic, and coherent beam of light by exciting atoms to a higher energy level and causing them to radiate their energy in phase.
• Laser
  Laser

  noun

  a type of dinghy, designed to be sailed by one person

laser

American  

[lay-zer] / ˈleɪ zər /

noun

Physics.

• lasers
  plural

1. a device that produces a nearly parallel, nearly monochromatic, and coherent beam of light by exciting atoms to a higher energy level and causing them to radiate their energy in phase.

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laser ¹ British  

/ ˈleɪzə /

noun

1. a source of high-intensity optical, infrared, or ultraviolet radiation produced as a result of stimulated emission maintained within a solid, liquid, or gaseous medium. The photons involved in the emission process all have the same energy and phase so that the laser beam is monochromatic and coherent, allowing it to be brought to a fine focus

2. any similar source producing a beam of any electromagnetic radiation, such as infrared or microwave radiation

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verb

1. to use a laser on (something), esp as part of medical treatment

2. (often foll by off) to remove (a tattoo, fat, etc) with laser treatment

Laser ² British  

/ ˈleɪzə /

noun

1. a type of dinghy, designed to be sailed by one person

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laser Scientific  

/ lā′zər /

1. Short for light amplification by stimulated emission of radiation. A device that creates and amplifies electromagnetic radiation of a specific frequency through the process of stimulated emission. The radiation emitted by a laser consists of a coherent beam of photons, all in phase and having the same polarization. Lasers have many uses, such as cutting hard or delicate substances, reading data from compact disks and other storage devices, and establishing straight lines in geographical surveying.

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laser Cultural  

1. A device that produces a very narrow, highly concentrated beam of light. Lasers have a variety of uses in such areas as surgery, welding and metal cutting, and sound and video recording and reproduction. The name is an acronym for l ight a mplification by s timulated e mission of r adiation.

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Closer Look

A laser emits a thin, intense beam of nearly monochromatic visible or infrared light that can travel long distances without diffusing. Most light beams consist of many waves traveling in roughly the same direction, but the phases and polarizations of each individual wave (or photon) are randomly distributed. In laser light, the waves are all precisely in step, or in phase, with each other, and have the same polarization. Such light is called coherent. All of the photons that make up a laser beam are in the same quantum state. Lasers produce coherent light through a process called stimulated emission. The laser contains a chamber in which atoms of a medium such as a synthetic ruby rod or a gas are excited, bringing their electrons into higher orbits with higher energy states. When one of these electrons jumps down to a lower energy state (which can happen spontaneously), it gives off its extra energy as a photon with a specific frequency. But this photon, upon encountering another atom with an excited electron, will stimulate that electron to jump down as well, emitting another photon with the same frequency as the first and in phase with it. This effect cascades through the chamber, constantly stimulating other atoms to emit yet more coherent photons. Mirrors at both ends of the chamber cause the light to bounce back and forth in the chamber, sweeping across the entire medium. If a sufficient number of atoms in the medium are maintained by some external energy source in the higher energy state—a condition called population inversion—then emission is continuously stimulated, and a stream of coherent photons develops. One of the mirrors is partially transparent, allowing the laser beam to exit from that end of the chamber. Lasers have many industrial, military, and scientific uses, including welding, target detection, microscopic photography, fiber optics, surgery, and optical instrumentation for surveying.

Other Word Forms

Noun Inflected Forms

• lasers
  plural

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Etymology

Origin of laser

1955–60; l(ightwave) a(mplification by) s(timulated) e(mission of ) r(adiation)

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Explanation

A laser is a focused beam of light used for many reasons, from eye surgery to gun scopes to laser pointers. The first laser was created more than 50 years ago. The word laser actually stands for "light amplification by stimulated emission of radiation," and the result is a powerful beam of light that happens to be very useful. Many people know lasers from science fiction movies, where aliens fire deadly lasers at Earth. Lasers aren't that dramatic in real life, but they are used in many ways, including surgery and light shows.

Example Sentences

See Examples For:

laser Laser lasers

Still, the Roadster’s debut had the air of an outdoor concert, complete with fog and red laser lights as content creators flanked a main stage.

From The Wall Street Journal ● Oct. 16, 2026

That means a lot of engineering is going into the small and nimble robot, including acoustic sensing that works like echolocation and a pulsing laser light to map the environment.

From The Wall Street Journal ● Oct. 16, 2026

Powerful laser microscopy revealed the mechanism: after a day or two of contact, the corals' tissues began fusing, creating a "nutrient highway" between the pair.

From Barron's ● Oct. 14, 2026

Outside of work, Kariem enjoyed creating products with his laser engraver and 3D printers, as well as cooking, watching anime and spending time with family and friends, according to his profile on the school's website.

From BBC ● Oct. 14, 2026

I can shoot a bow and arrow like a laser beam.

From "The Million Dollar Shot" by Dan Gutman

Another is Global Laser Enrichment, which is co-owned by Canadian uranium miner Cameco.

From The Wall Street Journal ● Sep. 21, 2026

Central Laser Facility in Oxfordshire - home to some of the most powerful lasers on Earth - will also be affected.

From BBC ● Jul. 9, 2026

The research was led by Chunlei Guo, a professor of optics and physics and a senior scientist at the University's Laboratory for Laser Energetics.

From Science Daily ● May 31, 2026

Venezuela's Laser Airlines will operate the same route from May 1.

From Barron's ● Apr. 30, 2026

The Laser began to roll across the floor.

From "Ralph S. Mouse" by Beverly Cleary

Lidar, for instance, is a scanning technique that employs lasers to detect hidden topological features.

From The Wall Street Journal ● Oct. 14, 2026

For more serious scarring, dermatologists can recommend more aggressive treatments such as lasers that probe deeper into the skin.

From Los Angeles Times ● Oct. 13, 2026

At a plant in Sherman, Texas, roughly the size of a football field, Cisco competitor Coherent makes lasers for iPhones — and for data centers.

From MarketWatch ● Sep. 19, 2026

Non-kinetic means could include lasers to blind satellites, or even electromagnetic or cyber jamming of their data links.

From Barron's ● Sep. 15, 2026

Getting to the *Modem surveys using lasers and state-of-the-art Doppler satellite transmissions have revised this measurement upward a mere 26 feet—to the currendy accepted altitude of 29,028 feet, or 8,848 meters.

From "Into Thin Air" by Jon Krakauer

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