[1] : The Collaborative International Dictionary of English v.0.48

unacceptable \un`accept"able\, a.
   not acceptable; not pleasing; not welcome; unpleasant;
   disagreeable; displeasing; offensive. --
   un`accept"ableness, n. -- un`accept"ably, adv.
   1913 webster
see also:
un`accept"ableness un`accept"ably 

[2] : WordNet (r) 2.0

unacceptable
     adj 1: not adequate to give satisfaction; "the coach told his
            players that defeat was unacceptable"
     2: not acceptable; not welcome; "a word unacceptable in polite
        society"; "an unacceptable violation of personal freedom"
        ant: acceptable
     3: used of persons or their behavior; "impossible behavior";
        "insufferable insolence" syn: impossible, insufferable,
         unsufferable
     4: not conforming to standard usage; "the following use of
        `access' was judged unacceptable by a panel of linguists;
        `you can access your cash at any of 300 automatic
        tellers'" syn: unaccepted
see also:
acceptable impossible insufferable unsufferable unaccepted 

[3] : Moby Thesaurus II by Grady Ward, 1.0

30 moby thesaurus words for "unacceptable":
   bad, disagreeable, discommendable, distasteful, exceptionable,
   ill-favored, illaudable, impossible, improper, inadmissible,
   inappropriate, indefensible, intolerable, objectionable, tasteless,
   unagreeable, unallowable, unasked, unbidden, uncommendable,
   undesirable, uninvited, unpleasant, unpraiseworthy, unsatisfactory,
   unsuitable, untenable, unwanted, unwelcome, wrong

Unacceptable >> U Words
Unacceptable, definition of term: Unacceptable
unacceptable_pag1.html