Glacial drift refers to all the materials, including boulders, sand, clay, and silt, deposited directly or indirectly by glaciers. It includes both till, which is deposited directly by the ice, and outwash, which is deposited by meltwater. Glacial drift is important for understanding past glacial movements, the history of glaciation, and the shaping of landscapes in glaciated regions.
Reference: Easterbrook, D. J. (1993). “Surface Processes and Landforms.” Prentice Hall.