maser. (mā`zər) , device for creation, amplification, and transmission of an intense, highly focused beam of high-frequency radio waves. The name maser is an acronym for m icrowave a mplification by s timulated e mission of r adiation, microwaves being radio waves of short wavelength, or high frequency. The maser is an oscillator oscillator, electronic, electronic circuit that produces an output signal of a specific frequency.