WordNet (r) 3.0 (2006):

borderland
    n 1: district consisting of the area on either side of a border
         or boundary of a country or an area; "the Welsh marches
         between England and Wales" [syn: borderland, border
         district, march, marchland]

Moby Thesaurus II by Grady Ward, 1.0:

87 Moby Thesaurus words for "borderland":
   Berlin wall, Pillars of Hercules, alentours, ambience, ambit,
   arena, back country, backwoods, bailiwick, bamboo curtain, beat,
   boondock, boondocks, border, border ground, borderlands, brush,
   bush country, bushveld, circle, circuit, circumambiencies,
   circumjacencies, circumstances, compass, context, demesne,
   department, domain, dominion, entourage, environing circumstances,
   environment, environs, field, forests, frontier, frontier post,
   gestalt, habitat, hemisphere, hinterland, iron curtain,
   judicial circuit, jurisdiction, march, marches, marchland, milieu,
   neighborhood, orb, orbit, outback, outpost, outposts, outskirts,
   pale, perimeter, periphery, precinct, precincts, province,
   purlieus, realm, round, situation, sphere, suburbs, surroundings,
   the bush, three-mile limit, timbers, total environment,
   twelve-mile limit, uninhabited region, up-country, vicinage,
   vicinity, virgin land, virgin territory, walk, wasteland,
   wild West, wilderness, wilds, woodlands, woods