'Unclean' in the Bible

Then I saw three unclean spirits like frogs coming from the dragon’s mouth, from the beast’s mouth, and from the mouth of the false prophet.

He cried in a mighty voice:It has fallen,Babylon the Great has fallen!She has become a dwelling for demons,a haunt for every unclean spirit,a haunt for every unclean bird,and a haunt for every unclean and despicable beast.