ice age 
noun
1A glacial episode during a past geological period. See glacial period.The most dramatic climate changes have occurred during the past 2 million years when the world entered the present ice age....
- The Time Machine zoomed its lead character into war torn London and past a new ice age.
- One thing that they need not concern themselves with is Global Warming causing the onset of the next ice age.
1.1 (the Ice Age) The series of glacial episodes during the Pleistocene period.He was ambivalent about whether or not they were ever filled by ice sheets during the Ice Age....
- Part I explores timber cutting from the end of the Ice Age through the medieval period.
- It was a very quick rate of change between the Ice Age and the warmer period.