'Open Country' in the Bible

The Ammonites came out and lined up for battle at the entrance of the [city] gate, but the Arameans of Zobah and Rehob and the men of Tob and Maacah were [stationed] by themselves in the field.

And the man said to David, Truly the men got the better of us, and came out against us into the open country, but we sent them back to the very doors of the town.