Any terrain on which avalanches occur (e.g., steep slopes and gullies.) This is a broader term than "avalanche path", which designates a specific area where an avalanche begins, runs, and ends.
In some ways avalanche terrain appears to be easy to define, in theory and indoors. Identifying it outdoors is often not so simple or obvious. Not all avalanche paths are large and obvious.
This glossary is a work in progress and is made possible by AlpenPro.