The Collaborative International Dictionary of English v.0.48:

Backwoods \Back"woods"\, n. pl. [Back, a. + woods.]
   The forests or partly cleared grounds on the frontiers.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "backwoods":
   back, back country, back of beyond, back-country, backcountry,
   backwash, backwater, backwood, backwoodsy, boondock, boondocks,
   borderland, brush, bush, bush country, bushveld, forests, frontier,
   hinterland, outback, outpost, sticks, sylvan, the bush, timbers,
   uninhabited region, up-country, virgin, virgin land,
   virgin territory, waste, wasteland, wild, wild West, wilderness,
   wilds, woodland, woodlands, woods