glacier
n. countablen. a huge, slow-moving river of ice that forms in very cold places like mountains or the poles.
n. a persistent body of dense ice that is constantly moving under its own weight. Forms where the accumulation of snow exceeds its ablation over many years.
The glacier moves a few inches every day.
Hikers must be careful of deep cracks in the ice when they walk across the glacier.
As global temperatures rise, the rapid melting of mountain glaciers contributes significantly to rising sea levels and alters the freshwater supply for local communities.
Borrowed from French glacier, from Franco-Provençal gllaciér, from Vulgar Latin *glaciārium, a derivative of Latin glaciēs (“ice”), of uncertain origin. First attested in English in 1744 per the OED.
Often used with verbs like 'retreat' or 'advance' to describe changes in size.