Webster Dictionary Definition of FLAT:

"Having a continuous horizontal surface without peaks or depressions." (This is the version I've always been comfortable with.)

Montana Definition of FLAT:

Any surface with a grade not as steep as the Rockies. (It appears North Dakotans use this definition as well.)

Climbed about a 1000 feet on Saturday...that's "Montana Flat".

Looking down from approx. 3000 feet toward the North Dakota border