Open country, esp. as opposed to woodland; a stretch of open land; a plain. In plural.

With the. The part of the countryside that is unenclosed or unfenced; land or ground clear of trees, buildings, or any other cover. Also (esp. in…

(with the; without plural) The level open country, as distinct from the mountains or woods, or the town; = champaign, n. 3.

Open country as opposed to hills, woods, etc.; country as opposed to town; = champaign, n. adj.