WordNet (r) 3.0 (2006):

Lowlands
    n 1: the southern part of Scotland that is not mountainous [syn:
         Lowlands, Lowlands of Scotland]

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "lowlands":
   agricultural region, alkali flat, alluvial plain, arable land,
   basin, black belt, bottomland, bushveld, campo, champaign,
   champaign country, citrus belt, coastal plain, corn belt,
   cotton belt, countryside, delta, desert, down, downs, dust bowl,
   farm belt, farm country, farmland, fell, flat, flat country,
   flatland, flats, fruit belt, grass roots, grass veld, grassland,
   grazing region, heath, highlands, lande, level, llano, lowland,
   lunar mare, mare, meadows and pastures, mesa, mesilla, moor,
   moorland, moors, open country, pampa, pampas, peneplain, plain,
   plains, plateau, playa, prairie, prairies, province, provinces,
   rural district, rustic region, salt flat, salt marsh, salt pan,
   savanna, sebkha, steppe, steppes, table, tableland, the country,
   the soil, the sticks, tobacco belt, tree veld, tundra, upland,
   uplands, vega, veld, weald, wheat belt, wide-open spaces, wold,
   woodland, woods and fields, yokeldom