From AMS Glossary
A usually dome-shaped mass of ice resting on rock and surrounded either by an ice shelf, or partly by an ice shelf and partly by the sea. No rock is exposed.
Armstrong, T., B. Roberts, and C. Swithinbank 1973. Illustrated Glossary of Snow and Ice. Scott Polar Research Institute, Special Pub. No. 4, 2d ed., The Scholar Press Ltd., Menston Yorkshire, UK.