Definition of "epochal"

epochal

adjective
comparative more epochal, superlative most epochal
1. Of or pertaining to an epoch.
2. (figurative) Highly important or significant; monumental, epoch-making.
  Quotations
  It had been an epochal decade for cancer epidemiology, but equally, an epochal decade for tobacco.
  2010, Siddhartha Mukherjee, The Emperor of All Maladies, Fourth Estate (2011), page 250