Real Dictionary

laser in American English
a device containing a substance the majority of whose atoms or molecules can be put into an excited energy state, allowing the substance to emit coherent light of a precise wavelength in an intense, narrow beam
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 in British English
to use a laser on (something), esp as part of medical treatment
noun: 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 tha
noun: a type of dinghy, designed to be sailed by one person

laser in Mechanical Engineering
noun: A laser is a device for producing a beam of light that can measure things or heat things at very high temperatures.