WordNet (r) 3.0 (2006):

undeveloped
    adj 1: not developed; "courses in interior design were rare and
           undeveloped"; "undeveloped social awareness" [ant:
           developed]
    2: undeveloped or unused; "vast unexploited (or undeveloped)
       natural resources"; "taxes on undeveloped lots are low" [syn:
       unexploited, undeveloped] [ant: exploited]

Moby Thesaurus II by Grady Ward, 1.0:

158 Moby Thesaurus words for "undeveloped":
   a novice at, a stranger to, adulterated, archaic, arrested,
   backward, behindhand, blemished, budding, callow, coarse, crude,
   damaged, defective, deficient, dewy, embryonic, erroneous,
   ever-new, evergreen, failing, fallible, faulty, firsthand,
   fledgling, found wanting, fresh, green, green as grass, growing,
   hypoplastic, ignorant, immature, impaired, imperfect, imprecise,
   impubic, impure, in arrear, in arrears, in default, in embryo,
   in ovo, in short supply, in the rough, inaccurate, inadequate,
   inchoate, incipient, incomplete, inexact, inexperienced, infant,
   ingenuous, innocent, intact, juicy, lacking, latent, maiden,
   maidenly, makeshift, mediocre, minor, missing, mixed, naive,
   needing, neoteric, nestling, new, new to, new-fledged, not perfect,
   off, original, oversimple, part, partial, patchy, persistent,
   potential, premature, pristine, raw, reductionistic, reductive,
   ripening, rough, roughcast, roughhewn, rude, rudimental,
   rudimentary, sappy, scant, scanty, scrappy, sempervirent, short,
   shy, simplistic, sketchy, stunted, tender, unaccustomed to,
   unacquainted with, unadult, unbeaten, unblown, unconversant,
   unconversant with, uncultivated, uncultured, uncut, underage,
   underdeveloped, uneven, unexperienced, unfamiliar with,
   unfashioned, unfinished, unfledged, unformed, unhandled, unhewn,
   uninitiated in, unlabored, unlicked, unmatured, unmellowed,
   unperfected, unpolished, unpracticed, unpracticed in, unprocessed,
   unprogressive, unrefined, unripe, unseasoned, unskilled in,
   unsound, unthorough, untouched, untreated, untried, untrodden,
   unused, unused to, unversed, unversed in, unworked, unwrought,
   vernal, virgin, virginal, wanting, young