Definitions of filthy:

• adjective:   disgustingly dirty; filled or smeared with offensive matter

  Example: "As filthy as a pigsty"

• adjective:   characterized by obscenity

  Example: "Had a filthy mouth"

• adjective:   thoroughly unpleasant

  Example: "Filthy (or foul or nasty or vile) weather we're having"

• adjective:   vile; despicable

  Example: "A filthy traitor"