any of a class of extremely large and luminous stars, such as Betelgeuse, which have expanded to a large diameter and are eventually likely to explode as supernovae
Compare giant star, white dwarf
supergiant in American English
(ˈsupərˌdʒaɪənt)
noun
an immense and extremely luminous star, as Betelgeuse or Antares, that has a diameter at least 100 times that of the sun and that is 100 to more than10,000 times as bright