WordNet (r) 3.0 (2006):

self-explanatory
    adj 1: needing no explanation

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "self-explanatory":
   apparent, clear, clear as crystal, comprehensible, crystal-clear,
   discernible, distinct, evident, explicit, express, indisputable,
   indubitable, manifest, noticeable, observable, obvious,
   open-and-shut, palpable, patent, perceivable, perceptible,
   perspicuous, plain, plain as day, seeable, self-contained,
   self-evident, self-explaining, tangible, to be seen,
   understandable, unmistakable, visible