Glacial means relating to or produced by glaciers or ice.

If you say that a person, action, or atmosphere is glacial, you mean that they are very unfriendly or hostile.

If you say that something moves or changes at a glacial pace, you are emphasizing that it moves or changes very slowly.

If you describe someone, usually a woman, as glacial, you mean they are very beautiful and elegant, but do not show their feelings.