maser

/ˈmeɪzər/
noun
  1. A device that produces a very narrow, intense beam of microwaves, similar to a laser but using microwaves instead of light.
    • The maser is used in radio telescopes to amplify weak signals from space.
    • Scientists built the first maser in the 1950s as a precursor to the laser.
    • Atomic clocks often use a hydrogen maser for extreme precision.