Gla·cial a.
 1. Pertaining to ice or to its action; consisting of ice; frozen; icy; esp., pertaining to glaciers; as, glacial phenomena.
 2. Chem. Resembling ice; having the appearance and consistency of ice; -- said of certain solid compounds; as, glacial phosphoric or acetic acids.
 Glacial acid Chem., an acid of such strength or purity as to crystallize at an ordinary temperature, in an icelike form; as acetic or carbolic acid.
 Glacial drift Geol., earth and rocks which have been transported by moving ice, land ice, or icebergs; bowlder drift.
 Glacial epoch or Glacial period Geol., a period during which the climate of the modern temperate regions was polar, and ice covered large portions of the northern hemisphere to the mountain tops.
 Glacial theory or Glacial hypothesis. Geol. See Glacier theory, under Glacier.

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 glacial epoch
      n 1: any period of time during which glaciers covered a large
           part of the earth's surface; "the most recent ice age
           was during the Pleistocene" [syn: ice age, {glacial
           period]
      2: from two million to 11 thousand years ago; extensive
         glaciation of the northern hemisphere; the time of human
         evolution [syn: Pleistocene, Pleistocene epoch]