Synonym of plain: land of relatively constant altitude, usually exclusive of forests, deserts, and wastelands. / (Ireland, informal) An urban region with many flats or apartments to rent.

plural of flatland

A terrain that varies little in elevation.

(Western US, especially in the Rocky Mountains) Anyone from the East; anyone from outside the Rockies. / (Appalachia) Any outsider to Appalachia.

plural of flatlander