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 ]

v. i. [ L. glaciatus, p. p. of glaciare to freeze, fr. glacies ice. ] To turn to ice. [ 1913 Webster ]

v. t. 1. To convert into, or cover with, ice. [ 1913 Webster ]

2. (Geol.) To produce glacial effects upon, as in the scoring of rocks, transportation of loose material, etc. [ 1913 Webster ]

Glaciated rocks, rocks whose surfaces have been smoothed, furrowed, or striated, by the action of ice. [ 1913 Webster ]

n. 1. Act of freezing. [ 1913 Webster ]

2. That which is formed by freezing; ice. [ 1913 Webster ]

3. The process of glaciating, or the state of being glaciated; the production of glacial phenomena. [ 1913 Webster ]

n. [ F. glacier, fr. glace ice, L. glacies. ] An immense field or stream of ice, formed in the region of perpetual snow, and moving slowly down a mountain slope or valley, as in the Alps, or over an extended area, as in Greenland. [ 1913 Webster ]

☞ The mass of compacted snow forming the upper part of a glacier is called the firn, or névé; the glacier proper consist of solid ice, deeply crevassed where broken up by irregularities in the slope or direction of its path. A glacier usually carries with it accumulations of stones and dirt called moraines, which are designated, according to their position, as lateral, medial, or terminal (see Moraine). The common rate of flow of the Alpine glaciers is from ten to twenty inches per day in summer, and about half that in winter. [ 1913 Webster ]

Glacier theory (Geol.), the theory that large parts of the frigid and temperate zones were covered with ice during the glacial, or ice, period, and that, by the agency of this ice, the loose materials on the earth's surface, called drift or diluvium, were transported and accumulated. [ 1913 Webster ]

a. Pertaining to, consisting of or resembling, ice; icy. Sir T. Browne. [ 1913 Webster ]

n. [ F. glacis; -- so named from its smoothness. See Glacier. ] A gentle slope, or a smooth, gently sloping bank; especially (Fort.), that slope of earth which inclines from the covered way toward the exterior ground or country (see Illust. of Ravelin). [ 1913 Webster ]