Added 10 October 2026 pleistocene noun Categories: TimeUncommon Words noun ! Definition from WordNet 3.1, Princeton University. More about pleistocene at Wordnik → Where our words come from → From two million to 11 thousand years ago; extensive glaciation of the northern hemisphere; the time of human evolution. Related Words: pliocenequaternarypliodiluviumpleistocenic Back to today's word