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[ley-zer] /ˈleɪ zər/
noun, Physics.
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.
Also called optical maser.
Origin of laser
1955-60; l(ightwave) a(mplification by) s(timulated) e(mission of) r(adiation) Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for laser
Contemporary Examples
Historical Examples
  • Or, I should say, the thing that is supposed to look like a laser component.

    The Foreign Hand Tie Gordon Randall Garrett
  • Therefore, he and his men were in absolute control of the men who controlled the laser.

    Where I Wasn't Going Walt Richmond
  • He handed the theodolite telescope and the laser milling-head to Paul.

    Where I Wasn't Going Walt Richmond
  • The earth shook and a great cloud of dust arose from the site, momentarily hiding the laser units.

    The Thirst Quenchers Rick Raphael
  • The laser operator fired and the light beam shot down into the earth, burning a narrow hole.

    The Thirst Quenchers Rick Raphael
British Dictionary definitions for laser


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
any similar source producing a beam of any electromagnetic radiation, such as infrared or microwave radiation
verb (transitive)
to use a laser on (something), esp as part of medical treatment
(often foll by off) to remove (a tattoo, fat, etc) with laser treatment
See also maser
Word Origin
C20: from light amplification by stimulated emission of radiation


trademark a type of dinghy, designed to be sailed by one person
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for laser

1960, acronym for "light amplification by stimulated emission of radiation," on pattern of 1955 MASER. A corresponding verb, lase, was coined 1962.

Online Etymology Dictionary, © 2010 Douglas Harper
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laser in Medicine

laser la·ser (lā'zər)
Any of several devices that convert incident electromagnetic radiation of mixed frequencies to discrete frequencies of highly amplified and coherent ultraviolet, visible, or infrared radiation; used in surgery to cut and dissolve tissue.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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laser in Science

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.

Our Living Language  : 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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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laser in Culture

laser definition

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 light amplification by stimulated emission of radiation.

The New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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