1.
landslide; landslip
The sliding or collapse of a mass of earth or rock down a slope, typically triggered by heavy rain or earthquakes.
2.
landslide (figurative); overwhelming victory
An overwhelming victory in an election or competition, by analogy with the unstoppable force of a landslide.
Also written as 地すべり. A common natural disaster in mountainous Japan, where heavy rainfall and earthquakes frequently trigger landslides. The figurative sense 地滑り的 (landslide-like) is frequently used in political and election coverage.