1. Specifically, the structural subdivision of the western USA between the Colorado Plateau to the east and the Sierra Nevada to the west. It is dominated by a series of block-faulted ranges and troughs which dissect it, rising above bajadas and alluvial plains which mask down-faulted units. Frequently the ranges are tilted blocks approximately 30–40 km across. Movement occurred initially in Miocene times, and then during the late Pliocene to Recent.

2. Generally, applied to landscapes having a series of tilted fault blocks that form long, asymmetric ranges separated by broad basins.