denotes "unclean, impure" (a, negative, and kathairo, "to purify"), (a) ceremonially, e.g., Acts 10:14,28; (b) morally, always, in the Gospels, of unclean spirits; it is translated "foul" in the AV of Mark 9:25; Revelation 18:2 , but always "unclean" in the RV. Since the word primarily had a ceremonial significance, the moral significance is less prominent as applied to a spirit, than when poneros, "wicked," is so applied. Cp. akatharsia, "uncleanness." See UNCLEAN.
Note: In Revelation 17:4 the best mss. have this word in the plural, RV, "the unclean things" (akathartes, "filthiness," in some mss.).