WordNet sense 1 (any substance considered disgustingly foul or unpleasant):

crud, skank

WordNet sense 2 (the state of being covered with unclean things):

dirt, grease, grime, grunge, soil, stain

WordNet sense 3 (a state characterized by foul or disgusting dirt and refuse):

filthiness, foulness, nastiness

WordNet sense 4 (an offensive or indecent word or phrase):

obscenity, vulgarism, dirty word