Meaning of LASER in English

LASER

n. a device that generates an intense beam of coherent monochromatic radiation in the infrared, visible, or ultraviolet region of the electromagnetic spectrum, by stimulated emission of photons from an excited source.

[ light amplification by stimulated emission of radiation: cf. MASER ]

Concise Oxford English dictionary.      Краткий оксфордский словарь английского языка.