'Foul' in the Bible

So the first angel went and poured out his bowl on the earth; and loathsome and malignant sores came on the people who had the mark of the beast and who worshiped his image.

Then I saw three foul spirits, resembling frogs, issue from the mouth of the Dragon, from the mouth of the Wild Beast, and from the mouth of the false Prophet.

And he cried mightily with a strong voice, saying, Babylon the great is fallen, is fallen, and is become the habitation of devils, and the hold of every foul spirit, and a cage of every unclean and hateful bird.

There will no longer exist anything that is cursed [because sin and illness and death are gone]; and the throne of God and of the Lamb will be in it, and His bond-servants will serve and worship Him [with great awe and joy and loving devotion];