Wiktionary
glacially
adv. 1 (context geology English) Through glacial action. (from 19th c.) 2 In a (literally or figuratively) icy manner; icily. (from 19th c.) 3 With the speed of a glacier; very slowly. (from 20th c.)
WordNet
glacially
adv. by a glacier; "glacially deposited material"
Usage examples of "glacially".
As the period ticked away glacially, Arthur Lomb buzzed him twice, squinting to see the title of the comic, then pursing lips in false concentration as he mimed browsing the half-empty shelves nearby, before stepping close enough for Dylan to hear him speak in an angry, clenched whisper.
Letitia declared glacially, roused from her book by my heroic though unparliamentary language.
Her own eyes, he noted, were still on the displays, her manner glacially calm.