Source : Webster's Revised Unabridged Dictionary (1913)

Moldiness \Mold"i*ness\, Mouldiness \Mould"i*ness\, n. [From
   {Moldy}.]
   The state of being moldy.

Source : WordNet®

moldiness
     n : the quality of smelling or tasting old or stale or mouldy
         [syn: {mustiness}, {must}]