Source : Webster's Revised Unabridged Dictionary (1913)

Loathsome \Loath"some\, a.
   Fitted to cause loathing; exciting disgust; disgusting.

         The most loathsome and deadly forms of infection.
                                                  --Macaulay.
   -- {Loath"some*ly}. adv. -- {Loath"some*ness}, n.

Source : WordNet®

loathsomeness
     n : the quality of being disgusting to the senses or emotions
         [syn: {repulsiveness}, {sliminess}, {vileness}]