A massive piece of ice of greatly varying shape, more than 5m above sea-level, which has broken away from a glacier (or an ice shelf), and which may be afloat or aground. Icebergs may be described as tabular, dome-shaped, sloping, pinnacled, weathered or glacier bergs (an irregularly shaped iceberg).
Icebergs are not sea ice. They originate from the ice mass of the Antarctic continent that has accumulated over many thousands of years. When they melt they add fresh water to the ocean.