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]

Moby Thesaurus II by Grady Ward, 1.0:

150 Moby Thesaurus words for "filth":
   Rabelaisianism, X-rated movie, abominableness, adulteration,
   atrociousness, awfulness, bad language, baseness, bawdiness,
   bawdry, beastliness, besmirchment, bestiality, billingsgate,
   blue language, blue movie, brutality, carrion, colorful language,
   contemptibleness, corruption, crud, cursing, cussing, dandruff,
   debasement, decay, defilement, degradation, despicableness,
   detestableness, direness, dirt, dirtiness, dirty language,
   dirty movie, dirty talk, disgustingness, dreadfulness, droppings,
   dung, dysphemism, effluent, egregiousness, erotic art,
   erotic literature, erotographomania, evil speaking, excrement,
   excreta, fescenninity, filthiness, filthy language, foul language,
   foul matter, foulness, fulsomeness, furfur, gangrene, garbage,
   grossness, guano, hatefulness, heinousness, horribleness,
   iconolagny, indecency, infamousness, leavings, lewdness,
   loathsomeness, lousiness, manure, mess, muck, mucus, nastiness,
   nefariousness, noisomeness, notoriousness, obnoxiousness,
   obscenity, odiousness, offal, offensiveness, ordure,
   outrageousness, perversion, pollution, pornographic art,
   pornographic literature, pornographomania, pornography,
   profane swearing, profanity, pus, putrefaction, putrescence,
   putrid matter, rankness, refuse, repulsiveness, ribaldry, rot,
   rottenness, rubbish, salaciousness, salacity, scandalousness,
   scatology, scurf, scurrility, scurviness, scuz, sewage, sewerage,
   sexploitation, shabbiness, shamefulness, shit, shoddiness,
   skin flick, slime, sludge, smut, smuttiness, snot,
   soft-core pornography, sordes, sordidness, squalidness, squalor,
   stag film, strong language, sullage, sullying, swearing, taint,
   terribleness, the pits, trash, uncleanness,
   unparliamentary language, unrepeatable expressions, vile language,
   vileness, vulgar language, vulgarity, worthlessness,
   wretchedness