- Also called glacial period, ice age. the geologically recent Pleistocene Epoch, during which much of the Northern Hemisphere was covered by great ice sheets.
- any one of the Permian, Carboniferous, Cambrian, or Precambrian glaciations.
- any period of time during which a large part of the earth’s surface was covered with ice, due to the advance of glaciers, as in the late Carboniferous period, and during most of the Pleistocene; glaciation
- (often capitals) the Pleistocene epoch