The Collaborative International Dictionary of English v.0.48:

Self-evident \Self`-ev"i*dent\, a.
   Evident without proof or reasoning; producing certainty or
   conviction upon a bare presentation to the mind; as, a
   self-evident proposition or truth. -- Self`-ev"i*dent*ly,
   adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

self-evident
    adj 1: evident without proof or argument; "an axiomatic truth";
           "we hold these truths to be self-evident" [syn:
           axiomatic, self-evident, taken for granted(p)]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "self-evident":
   absolute, actual, admitting no question, apparent, axiomatic,
   clear, clear as crystal, clear-cut, confirmable, crystal-clear,
   definite, demonstrable, demonstratable, discernible, distinct,
   evident, explicit, express, factual, historical, inappealable,
   incontestable, incontrovertible, indisputable, indubitable,
   inescapable, irrefragable, irrefutable, manifest, noticeable,
   observable, obvious, open-and-shut, palpable, patent, perceivable,
   perceptible, perspicuous, plain, plain as day, provable,
   proverbial, real, seeable, self-explaining, self-explanatory,
   tangible, testable, to be seen, true, unanswerable, unconfutable,
   undeniable, unimpeachable, unmistakable, unquestionable,
   unrefutable, verifiable, visible



The Devil's Dictionary (1881-1906):

SELF-EVIDENT, adj.  Evident to one's self and to nobody else.