1. A device that generates or amplifies electromagnetic radiation, especially microwaves, of a coherent wavelength by stimulated emission.
2. A natural object or region of space that acts like a maser, as a star-forming region of intersellar space.
[m(icrowave) a(mplification by) s(timulated) e(mission of) r(adiation).]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.