intermountain

adjective

in·​ter·​moun·​tain ˌin-tər-ˈmau̇n-tᵊn 

: existing between mountains

intermountain streams

intermountain towns

Yet recreation funding for Colorado and other intermountain states stayed flat.

—Penelope Purdy

The earthquake hazard is highest on the West Coast, intermountain West and in regions of the Central and Eastern U.S. …

—Elaine Pittman

Word History

First Known Use

1854, in the meaning defined above