An iceberg
It's called "calving"
iceberg
An Iceberg.
When a piece of a glacier breaks off, it is called calving. This can result in the formation of icebergs.
An ice that breaks off a glacier and floats away is called an iceberg.
A glacier is a piece of ice.
A large detached piece of a glacier is called an iceberg. The process by which this happens is called calving.There isn't really a term for a detached piece of an iceberg. See related question.
A glacier is older than an iceberg, because an iceberg is a piece of ice that fell off a glacier.
A floating piece of ice is called an iceberg if it is large and mostly submerged, or an ice floe if it is smaller and more flat or thin.
malaspina glacier
A frozen river is called a frozen river. Rivers that normally flow as liquid water, are called frozen rivers when they become frozen.
The tip of a glacier is called the glacier terminus or glacier snout. It is the furthest point reached by the glacier as it flows downhill.