ice dam

(rivers, glaciers) an obstruction to the flow of a river caused by the flow of a glacier across its course

(rivers) 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

(roofing) 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.

(roofing) Ellipsis of ice dam membrane. A plastic protection membrane applied to rooves to prevent ice buildup from backing water through roof sheeting