1. 
[syn: disgusting, disgustful, distasteful, foul, loathly, loathsome, repellent, repellant, repelling, revolting, skanky, wicked, yucky]
The Collaborative International Dictionary of English v.0.48:
yucky \yuck"y\, a.
   Repugnant or distasteful. [slang]
   Syn: disgusting, disgustful, distasteful, loathly, loathsome,
        repellent, repellant, repugnant, revolting.
        [PJC + WordNet 1.5]
WordNet (r) 3.0 (2006):
yucky
    adj 1: highly offensive; arousing aversion or disgust; "a
           disgusting smell"; "distasteful language"; "a loathsome
           disease"; "the idea of eating meat is repellent to me";
           "revolting food"; "a wicked stench" [syn: disgusting,
           disgustful, distasteful, foul, loathly,
           loathsome, repellent, repellant, repelling,
           revolting, skanky, wicked, yucky]
Moby Thesaurus II by Grady Ward, 1.0:
38 Moby Thesaurus words for "yucky":
   awful, bad, barfy, beastly, brackish, cloying, disgusting, fetid,
   foul, fulsome, high, icky, maggoty, mawkish, mucky, nasty,
   nauseant, nauseating, nauseous, noisome, noxious, offensive,
   overripe, poisonous, rancid, rank, rebarbative, repellent,
   repugnant, revolting, rotten, sickening, spoiled, stinking,
   unappetizing, vile, vomity, weevily