Definition of Idaho
- a state in the northwestern US that borders on the Canadian province of British Columbia on the north and that includes part of the Rocky Mountains; population 1,523,816 (est. 2008); capital, Boise; statehood, July 3, 1890 (43). It was explored by Lewis and Clark in 1805 and was crossed by the Oregon Trail that ended at Fort Vancouver in Washington.
noun & adjective