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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  

[ley-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

Etymology

Origin of laser

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

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

The material is essential for turning electrical signals into laser light.

From MarketWatch ● Sep. 19, 2026

A cuirass from 2010’s crystallization collection—a 3-D-printed polyamide using selective laser sintering—is part ammonite, part “Alien,” beautiful and terrifying.

From The Wall Street Journal ● Sep. 19, 2026

When laser light was directed at the structures, the resulting diffraction patterns formed distinctive pinwheel-like shapes.

From Science Daily ● Sep. 15, 2026

The studies evaluated 12 different approaches, including laser therapy, electrical stimulation, knee braces, insoles, kinesiology tape, water-based therapy, exercise, and ultrasound.

From Science Daily ● Sep. 15, 2026

Last year we played laser tag in the park.

From Absolutely Almost by Lisa Graff

Laser light continuously travels through both parts of the system, helping the desired optical states form and remain stable.

From Science Daily ● Aug. 24, 2026

Laser beams that destroy missiles can be added.

From The Wall Street Journal ● Aug. 2, 2026

“The race to build AI infrastructure has created urgent demand for providers who can deliver at speed without sacrificing reliability,” says Ross Laser, Magnetar’s president and co-founder.

From The Wall Street Journal ● Jun. 10, 2026

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

From Barron's ● Apr. 30, 2026

“Wait till your relatives see you riding around in a Laser XL7,” remarked Matt.

From "Ralph S. Mouse" by Beverly Cleary

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

Excimer lasers are used in semiconductor manufacturing, but the government’s work on laser fusion for energy and managing the country’s nuclear weapons stockpile shifted to glass lasers instead.

From The Wall Street Journal ● Sep. 10, 2026

The company is even investigating lasers and ultrasound as potentially speedier methods of slicing pizzas than a traditional knife blade.

From BBC ● Aug. 27, 2026

Slowly he raised his head, his eyes locked onto Maddie like lasers.

From "Book Scavenger" by Jennifer Chambliss Bertman

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