/ ˈgleɪʃl; NAmE ; ˈgleɪsiəl/ adjective
1.
[ usually before noun ] ( geology ) connected with the Ice Age :
the glacial period (= the time when much of the northern half of the world was covered by ice)
2.
( technical ) caused or made by glaciers ; connected with glaciers :
a glacial landscape
glacial deposits / erosion
3.
( formal ) very cold; like ice
SYN icy :
glacial winds / temperatures
4.
( formal ) ( used about people ) cold and unfriendly; not showing feelings
SYN icy :
Her expression was glacial.
Relations between the two countries had always been glacial.
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WORD ORIGIN
mid 17th cent.: from French , or from Latin glacialis icy, from glacies ice.