The slow, deformation and densification of snow under the influence of gravity. Not to be confused with collasping
Settlement and Sintering:

A newborn, snowflake that falls out of the sky doesn't stay that way for long. As soon as it lands on the snow surface it begins a rapid process of change. Just like people, as a snowflake ages, its beautiful, angular shape becomes progressively more rounded through time and it forms bonds with its neighbors. In people, it's called growing up; in the snowpack it's called "sintering"--forming bonds with neighboring crystals to create the fabric of the snowpack.

As sintering progresses, the snow becomes denser and stronger, which we call "settlement." Sometimes you will hear people incorrectly use the term settlement to describe the catastrophic collapse of a snowpack that often makes a giant "whoomph" sound, as in, "Hey, did you hear that settlement? Maybe we should get out of here." Instead, we call these collapses or "whoomphing", which, believe it or not, is actually the technical term for a collapsing snowpack. It sounds funny but it's a great description. Settlement is the SLOW deformation of the snow as it densifies and sags under the influence of gravity.

New, fluffy snow settles relatively quickly, within minutes to hours and it settles much more quickly at warm temperatures than in cold temperatures. We often think of settlement within the new snow as a sign of stability (at least within the new snow) because it means that the new snow is rapidly becoming stronger. When new snow settles, it forms "settlement cones" around trees and bushes where the snow bonds to the bush which props up the snow, like a circus tent.

Additional Terms:
Anchors Hard Slab Avalanche Slide
Aspect High Danger Sluff
Avalanche High Marking Snowpit
Avalanche Path Isothermal Soft Slab Avalanche
Avalanche Transceiver Layer, Snow Stability
Bed Surface Leeward Stability Test
Collapse Loading Starting Zone
Concave Slope Loose Snow Avalanche Stepping Down
Considerable Danger Low Avalanche Hazard Sun Crust
Convex Slope Melt-Freeze Snow Surface Hoar
Cornice Metamorphism, Snow Sympathetic Trigger
Corn Snow Moderate Danger Temperature Gradient
Couloir Persistent Weak Layers Terrain Trap
Cross Loading Point-Release Track
Crown Face Probe Trigger
Danger Ratings Propagation Trigger Point
Deep Slab Avalanche Rain Crust Upside-Down Storm
Density, Snow Remote Trigger Weak Layer
Depth Hoar Rime Weak Interface
Dry Snow Avalanche Runout Zone Wet Snow Avalanche
Extreme Danger Sastrugi Windward
Faceted Snow Settlement Wind Loading
Fracture Ski or Slope Cut Wind Slab
Glide Skinning, Skin Track Whumpf
Graupel Slab