adjective
glacial
GLAY-shul/ˈɡleɪʃl/
Extremely slow, like the movement of a glacier.
The computer task makes glacial progress while the waiting user falls asleep.

Etymology
From icy and glacier-related, the word came to evoke the extremely slow movement of glaciers.
More examples
- Negotiations move at a glacial speed.
- The line makes glacial progress toward the door.
Forms
glacial
Similar words
- slow
- A neutral general description of low speed.
- sluggish
- Suggests a lack of energy or responsiveness.