1. extremely cold
2. showing that you are angry or unfriendly
3. extremely slow
4. created by glaciers millions of years ago
Origin and usage
The word glacial came into English from French in the mid 17th century. It derives from a Latin word ‘glacialis’, which means ‘icy’.
Although the core meaning of the adjective glacial is the one relating to glaciers, its placement at number four in the Macmillan Dictionary entry shows that it is in fact the least frequently used in everyday speech and writing (in technical writing it is a different story, of course). Instead we are far more likely to use the figurative meanings, all of which derive from the core meaning, both for the adjective and the related adverb glacially. So a glacial wind is extremely cold, as a glacier is. Something that moves with glacial slowness resembles the movement of a glacier, which can take a day or even longer to move one metre. And if someone gives you a glacial look or stare, their feelings towards you are probably as cold as ice.
“By all means, move at a glacial pace. You know how that thrills me.”
(Meryl Streep in The Devil Wears Prada)