high country

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An area of land formed or lying above the piedmont and below the timberline.

Wiktionary

1. n. Terrain that is at a relatively high elevation — generally, higher than foothills but not above the timberline — consisting of mountainous areas or elevated expanses of plain.

WordNet 3.0

1. n. an area lying above the piedmont but below the timberline