A supernova actually is something that happens. Ever heard the term "red giant" or "white dwarf"? That is generally used to describe the qualitative characteristics of a star. In it's different life stages.
The exact definition of a super nova:
The explosion caused when a massive star, at least 8 times the Sun's mass, dies (exhausts its fuel) and collapses. If the original star is less than 20 solar masses, the supernova will leave behind a neutron star. Heavier stars will collapse into black holes. Supernova explosions are among the most energetic events in the Universe, and they forge the heavy elements such as carbon, oxygen, and silicon.
www.gsfc.nasa.gov/gsfc/spacesci/pictures/2003/0702pulsarspeed/0702ssu_glossary.htm