WordNet (r) 3.0 (2006):

naturistic
    adj 1: in accord with naturism

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "naturistic":
   bald, bare, bare-ass, general, gymnosophical, in native buff,
   in puris naturalibus, in the altogether, in the buff, in the raw,
   naked, natural, naturalistic, normal, nude, nudist, orderly,
   peeled, raw, realistic, stark-naked, typical, unexceptional,
   with nothing on, without a stitch