1 - A layer within a snowpack which has been wetted by free water percolating through the snow. Sometimes any weak layer or cohesionless layer which has acted as the basal zone in a slab avalanche.
2 - A layer with weak internal strength and/or poor bonding to adjacent layers which facilitates mechanical failure within the snow pack. A recognizable lubricating layer may or may not be present in an avalanche.
This glossary is a work in progress and is made possible by AlpenPro.