ice pack

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A floating mass of compacted ice fragments.
• noun A folded sac filled with crushed ice and applied to sore or swollen parts of the body to reduce pain and inflammation.

from The Century Dictionary.

• noun A great field of ice, consisting of separate masses packed together or lying closely adjacent to one another, as in the arctic seas.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a large floating mass of ice; pack ice
• noun a pack of crushed ice applied to the body in order to reduce pain or inflammation
• noun a plastic sac of silicone that can be cooled in a freezer and then used in a cool bag

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a waterproof bag filled with ice: applied to the body (especially the head) to cool or reduce swelling
• noun a large expanse of floating ice