WordNet (r) 3.0 (2006):

unappetizing
    adj 1: not appetizing in appearance, aroma, or taste [syn:
           unappetizing, unappetising] [ant: appetising,
           appetizing]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "unappetizing":
   bitter, disagreeable, dislikable, displeasing, distasteful, flat,
   flavorless, foul-tasting, ill-flavored, insipid, savorless, sour,
   tasteless, thankless, ugly, unalluring, unappealing, unattractive,
   undelectable, undelicious, undesirable, unengaging, unenjoyable,
   uninviting, unlikable, unpalatable, unpleasant, unpleasing,
   unsavory, untasteful, untasty, unwelcome