The Collaborative International Dictionary of English v.0.48:

Objectionable \Ob*jec"tion*a*ble\, a.
   Liable to objection; likely to be objected to or disapproved
   of; offensive; as, objectionable words. --
   Ob*jec"tion*a*bly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

objectionable
    adj 1: causing disapproval or protest; "a vulgar and
           objectionable person" [syn: objectionable, obnoxious]
    2: liable to objection or debate; used of something one might
       take exception to; "a thoroughly unpleasant highly
       exceptionable piece of writing"; "found the politician's
       views objectionable" [syn: exceptionable, objectionable]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "objectionable":
   abhorrent, abominable, base, beastly, below contempt,
   beneath contempt, censurable, contemptible, crude, despicable,
   detestable, disagreeable, discommendable, disgusting, distasteful,
   exceptionable, execrable, fetid, forbidding, foul, fulsome, gross,
   hateful, heinous, ignoble, ill-favored, illaudable, impossible,
   inadmissible, indefensible, intolerable, invidious, loathsome,
   malodorous, mephitic, miasmal, miasmic, nasty, nauseating, noisome,
   noxious, obnoxious, obscene, odious, offensive, rebarbative,
   repellent, reprehensible, repugnant, repulsive, revolting,
   sickening, stinking, unacceptable, uncommendable, undesirable,
   unfit, unpleasant, unpraiseworthy, unsuitable, untenable, unwanted,
   unwelcome, vile