Definition of "maser" [ma•ser]

• Any of several devices that amplify or generate electromagnetic waves, especially microwaves. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "It superseded the word maser, coined in 1950, meaning Microwave Amplification by Stimulated Emission of Radiation."
• "The result was a "maser" - like a laser, but using microwaves instead of visible light."
• "Ramsey and co-workers have also developed the hydrogen maser, which is at present our most stable source of electromagnetic radiation."