The Collaborative International Dictionary of English v.0.48:

Filth \Filth\ (f[i^]lth), n. [OE. filthe, ful[eth]e, AS.
   f[=y]l[eth], fr. f[=u]l foul; akin to OHG. f[=u]lida. See
   Foul, and cf. File.]
   1. Foul matter; anything that soils or defiles; dirt;
      nastiness.
      [1913 Webster]

   2. Anything that sullies or defiles the moral character;
      corruption; pollution.
      [1913 Webster]

            To purify the soul from the dross and filth of
            sensual delights.                     --Tillotson.
      [1913 Webster]

   Filth disease (Med.), a disease supposed to be due to
      pollution of the soil or water.
      [1913 Webster]

WordNet (r) 3.0 (2006):

filth
    n 1: any substance considered disgustingly foul or unpleasant
         [syn: filth, crud, skank]
    2: the state of being covered with unclean things [syn: dirt,
       filth, grime, soil, stain, grease, grunge]
    3: a state characterized by foul or disgusting dirt and refuse
       [syn: filth, filthiness, foulness, nastiness]
    4: an offensive or indecent word or phrase [syn: obscenity,
       smut, vulgarism, filth, dirty word]