What term describes a glacially deposited rock unlike the local bedrock?

A glacially deposited rock unlike the local bedrock is called a glacial erratic. Glaciers can pluck rocks from their original outcrops, carry them embedded in or on top of the ice, and leave them behind when the ice melts.

Erratics may be small pebbles or enormous boulders. Geologists identify them by comparing their mineral composition and texture with exposed bedrock elsewhere. If a distinctive boulder matches a source hundreds of kilometres away, it can reveal the direction and extent of ancient glacier movement.

The word “erratic” comes from a Latin term meaning “to wander,” reflecting the rock's unexpected location. Erratics became especially important evidence for the 19th-century acceptance of past ice ages. Before glacial explanations gained support, large foreign rocks scattered across landscapes were difficult for geologists to explain.

A dropstone is related but more specific: it is a rock released from floating ice into marine or lake sediment. Talus is loose rock accumulated below a cliff, while bedrock is the solid rock underlying an area. Those terms therefore do not best match the question's general definition.