Mass movement is a term used to describe a large and rapid movement of earth materials, such as rocks, soil, and other debris. There are several synonyms for this term, including landslides, slope failures, rockslides, debris flows, mudflows, and rockfall. Landslides and slope failures are both types of mass movements that occur on steep slopes, while rockslides and debris flows refer specifically to the movement of rocks and debris. Mudflows are similar to debris flows, but are composed primarily of water and sediment, while rockfall refers to the single, sudden fall of rocks. These synonyms are important for describing and categorizing different types of mass movements.