The Collaborative International Dictionary of English v.0.48:

Unregenerate \Un`re*gen"er*ate\, Unregenerated
\Un`re*gen"er*a`ted\, a.
   Not regenerated; not renewed in heart; remaining or being at
   enmity with God.
   [1913 Webster]

WordNet (r) 3.0 (2006):

unregenerate
    adj 1: tenaciously unwilling or marked by tenacious
           unwillingness to yield [syn: stubborn, obstinate,
           unregenerate] [ant: docile]
    2: not reformed morally or spiritually; "unregenerate human
       nature"; "unregenerate conservatism" [syn: unregenerate,
       unregenerated] [ant: regenerate]
    3: unrepentant and incapable of being reformed; "an unregenerate
       criminal" [syn: unreformable, unregenerate]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "unregenerate":
   balking, balky, bigoted, bulldogged, bulletheaded, bullheaded,
   case-hardened, damned, dogged, dogmatic, fanatic, fleshly, godless,
   graceless, hardheaded, headstrong, incorrigible, intolerant,
   irreclaimable, irredeemable, irreformable, lost, mulish, mundane,
   nonsacred, obstinate, opinionated, overzealous, past praying for,
   persevering, pertinacious, pigheaded, profane, reprobate, restive,
   secular, self-willed, set, shriftless, stiff-necked, strong-willed,
   strongheaded, stubborn, sulky, sullen, temporal, tenacious,
   unblessed, unconverted, uncooperative, unhallowed, unholy,
   unredeemable, unredeemed, unsacred, unsanctified, willful,
   worldly