The Collaborative International Dictionary of English v.0.48:

hinterland \hin"ter*land`\, n. [G.; hinter behind + land land.]
   a remote and undeveloped area; originally, the land or region
   lying behind the coast district. The term is used esp. with
   reference to the so-called

   doctrine of the hinterland, sometimes advanced, that
      occupation of the coast supports a claim to an exclusive
      right to occupy, from time to time, the territory lying
      inland of the coast.

   Syn: backwoods, back country, boondocks.
        [Webster 1913 Suppl. + WordNet 1.5]

WordNet (r) 3.0 (2006):

hinterland
    n 1: a remote and undeveloped area [syn: backwoods, back
         country, boondocks, hinterland]

Moby Thesaurus II by Grady Ward, 1.0:

85 Moby Thesaurus words for "hinterland":
   airspace, area, arena, back, back country, backcountry, backdrop,
   background, backwash, backwater, backwoods, belt, boondock,
   boondocks, borderland, brush, bush, bush country, bushveld,
   confines, continental shelf, corridor, country, department,
   distance, district, division, environs, field, forests, frontier,
   ground, heartland, inland, inlands, interior, land, locale,
   midland, midlands, milieu, mise-en-scene, neighborhood,
   offshore rights, outback, outpost, part, parts, place, precincts,
   premises, purlieus, quarter, rear, region, salient, scene, section,
   setting, soil, space, stage, stage set, stage setting, sticks,
   terrain, territory, the bush, theater, three-mile limit, timbers,
   twelve-mile limit, uninhabited region, up-country, vicinage,
   vicinity, virgin land, virgin territory, wasteland, wild West,
   wilderness, wilds, woodlands, woods, zone