a. [ L. glacialis, from glacies ice: cf. F. glacial. ] 1. Pertaining to ice or to its action; consisting of ice; frozen; icy; esp., pertaining to glaciers; as, glacial phenomena. Lyell. [ 1913 Webster ]

2. (Chem.) Resembling ice; having the appearance and consistency of ice; -- said of certain solid compounds; as, glacial phosphoric or acetic acids. [ 1913 Webster ]

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. [ 1913 Webster ]

n. One who attributes the phenomena of the drift, in geology, to glaciers. [ 1913 Webster ]

a. (Geol.) (a) Formed or occurring after the last glacial epoch of the Pleistocene period, or at a locality within the area of Pleistocene glaciation after the final disappearance of the glacier from the locality. (b) Of, pertaining to, or designating, an epoch after the last Glacial and before the Terrace epoch. [ R. ] [ Webster 1913 Suppl. ]

a. (Geol.) Prior to the glacial or drift period. [ 1913 Webster ]

a. Pertaining or belonging to the under side of a glacier; being beneath a glacier; as, subglacial streams. [ 1913 Webster ]