A laser is a device which amplifies electromagnetic radiation by the process of stimulated emission. The term is generally applied only to the amplification of radiation at or above infrared frequencies (see also maser). While amplification by stimulated emission is the only necessary criterion for a laser, the most familiar devices are those which employ some type of feedback and are referred to as laser oscillators.
The term laser is an acronym for Light Amplification by Stimulated Emission of Radiation. It is a modification of an earlier term, maser (Microwave Amplification by Stimulated Emission of Radiation).
The forms "to lase" and "lasing" are commonly used to describe the action of laser.
May 16, 1960 – The world’s first successful laser is demonstrated by Theodore H. Maiman, a junior employee of the Hughes Research Laboratories in Malibu, California. 
- Maiman, T. H. “Stimulated Optical Radiation in Ruby.” Nature 187, 493-494, 1960.