glacially

adverb3

1. •
   Through glacial action.
2. •
   With the speed of a glacier; very slowly.

   • The daunting problem is that the incidence of tuberculosis has declined only glacially (at a rate of 1.0 to 1.5% per year) and in some places may be increasing. — 2018
3. •
   In a (literally or figuratively) icy manner; icily.

   • ‘Monsieur,’ Louis XV glacially remarked to Choiseul days before the dénouement, ‘I told you that I did not want war.’ — 2002