New answers tagged geography
While it doesn't appear as authoritative as @Ian's reference, I found that the Natural Earth label areas shapefile contains very rough delineations, which were sufficient for my purposes.
UNEP-WCMC came up with a definition using altitude and slope and a few other criteria that resulted in 7 classes all defined as mountainous regions. The info below is from the 2002 version. Data: http://www.arcgis.com/home/item.html?id=a068913914cd4fecb302b9207a532d1a Definition of mountainous regions: ...
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