any of a number of starlike celestial objects that emit immense amounts of light and, often, radio waves, characterized by having spectral lines with very large redshifts: quasars are thought to be the most distant and oldest observable objects in the universe
Origin:
< quas(i-stell)ar (radio source)
See quasar in American Heritage Dictionary 4
noun
An extremely distant, and thus old, celestial object whose power output is several thousand times that of our entire galaxy.