WordNet (r) 3.0 (2006):

messiness
    n 1: a state of confusion and disorderliness; "the house was a
         mess"; "she smoothed the mussiness of the bed" [syn:
         mess, messiness, muss, mussiness]
    2: the trait of being untidy and messy [syn: untidiness,
       messiness] [ant: neatness, tidiness]

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "messiness":
   amorphia, amorphism, amorphousness, anarchy, bad job, blowziness,
   blurriness, botch, bungling, carelessness, chaos, chintziness,
   confusion, dinginess, dirtiness, disorder, dowdiness, entropy,
   formlessness, frowziness, frumpishness, fuzziness, griminess,
   grubbiness, haphazardness, haziness, immundity, impurity,
   indecisiveness, indefiniteness, indeterminateness, loose ends,
   looseness, miriness, mistiness, muddiness, negligence, obscurity,
   orderlessness, sad work, scruffiness, seediness, shabbiness,
   shapelessness, shoddiness, slapdash, slatternliness,
   slipshoddiness, slipshodness, sloppiness, slovenliness,
   slovenly performance, slovenry, sluttishness, sordidness,
   squalidness, squalor, tackiness, tawdriness, uncleanliness,
   uncleanness, unclearness, unneatness, unpureness, untidiness,
   vagueness