The term 'fallen rock' can be summarized by the crossword solution 'SCREE, ' which is a type of rock fragment that accumulates at the base of mountains or cliffs. SCREE is composed of broken rock, such as shale, sandstone, and limestone, that has been eroded away from the cliff face by weathering and gravity. It is usually found in areas with steep slopes and is often used to stabilize the soil and prevent further erosion.