mass extinction

mass extinction (countable and uncountable, plural mass extinctions)

1. (evolutionary theory, geology) A sharp decrease in the total number of species in a relatively short period of time; specifically, a loss of ∼75% of all species on the planet over a geologically interval of less than 3 million years, as a result of a mass extinction event.
   • 2020, Jonathan Elmore, editor, Fiction and the Sixth Mass Extinction, Rowman & Littlefield, →ISBN, page 4:

     Preceded by five other mass extinctions and many more small extinction events, the mass extinction currently underway is, on the one hand, like all the others in that it is nothing other than a significant reduction in the number of individual organisms inhabiting the planet and at the same time a significant reduction in the diversity of species made up by those individual organisms.

• mass extinction event
• extinction event
• extinction level event