The Collaborative International Dictionary of English v.0.48:

Unambiguous \Unambiguous\
   See ambiguous.

WordNet (r) 3.0 (2006):

unambiguous
    adj 1: having or exhibiting a single clearly defined meaning;
           "As a horror, apartheid...is absolutely unambiguous"-
           Mario Vargas Llosa [ant: ambiguous]
    2: admitting of no doubt or misunderstanding; having only one
       meaning or interpretation and leading to only one conclusion;
       "unequivocal evidence"; "took an unequivocal position"; "an
       unequivocal success"; "an unequivocal promise"; "an
       unequivocal (or univocal) statement" [syn: unequivocal,
       univocal, unambiguous] [ant: ambiguous, equivocal]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "unambiguous":
   absolute, ambiguous, apodictic, apparent, bound, categorical,
   certain, clean-cut, clear, clear and distinct, clear as crystal,
   clear as day, clear-cut, coherent, conclusive, connected,
   consistent, crisp, crystal, crystal-clear, crystalline, decisive,
   defined, definite, definitive, determinate, direct, distinct,
   evident, explicit, express, ineluctable, inevitable, limpid,
   loud and clear, lucid, luminous, manifest, necessary, obscure,
   obvious, palpable, patent, pellucid, perfectly sure, perspicuous,
   plain, positive, predestined, predetermined, simple, specific,
   straightforward, sure, sure-enough, translucent, transparent,
   transpicuous, true, unconfused, unequivocal, univocal,
   unmistakable, well-defined