What is the meaning of Ice_dam?

An obstruction to the flow of a river caused by the flow of a glacier across its course.

An obstruction to the flow of a river caused by the concatenation of surface ice into a ridge that rises above and sinks below the surface causing a blockage, occurring frequently during spring breakup season.

A mass of ice formed at the transition from a warm to a cold roof surface, frequently formed by refreezing meltwater at the overhang of a steep roof, causing ice and water to back up under roofing materials.

Ellipsis of ice dam membrane.

Source: wiktionary.org