- a large area of floating ice formed over a period of many years and consisting of pieces of ice driven together by wind, current, etc.
- a large area of floating ice, usually occurring in polar seas, consisting of separate pieces that have become massed togetherAlso called: ice pack
- The floating sea-ice cover of the polar regions. Driven by winds and ocean currents, pack ice is a mixture of ice fragments of varying size and age that are squeezed together and cover the sea surface with little or no open water. At maximum expansion during the winter, pack ice covers about five percent of Arctic waters and about eight percent of Antarctic waters.