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1. 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
2. the Pleistocene epoch
glacial period[¦glā·shəl ′pir·ē·əd]
Any of the geologic periods which embraced an ice age; for example, the Quaternary period may be called a glacial period.
Generally, an interval of geologic time which was marked by a major equatorward advance of ice.