A floe is a sheet of ice floating on the sea. People almost always say ice floe, not floe alone. Picture a flat piece of ice, like a broken plate, drifting on cold water — not a tall hill of ice. That taller ice is an iceberg, a different thing. A floe can be small enough to see across, or huge, like a field. Ships in very cold seas have to watch for them. The word belongs to sea ice; you would not use it for ice on a pond in a park unless you were stretching it. It is a quiet word: sailors, scientists, and news about polar ice.