Unclean - Vine's Expository Dictionary of New Testament Words
Unclean
[ A-1,Adjective,G169, akathartos ]unclean, impure" (a, negative, kathairo, "to purify"), is used
(a) of "unclean" spirits, frequently in the Synoptists, not in John's gospel; in Acts 5:16; Acts 8:7; Revelation 16:13; Revelation 18:2 (in the 2nd clause the birds are apparently figurative of destructive satanic agencies);
(b) ceremonially, Acts 10:14, Acts 10:28; Acts 11:8; 1 Corinthians 7:14;
(c) morally, 2 Corinthians 6:17, including
(b), RV; "no unclean thing;" Ephesians 5:5; Revelation 17:4, RV, "the unclean things" (AV follows the text which have the noun akathartes, "the filthiness").
[ A-2,Adjective,G2839, koinos ]
"common," is translated "unclean" in Romans 14:14 (thrice); in Revelation 21:27, RV (AV, "that defileth," follows the inferior texts which have the verb koinoo: See B). See COMMON, DEFILE, C, UNHOLY, No. 2.
[ B-1,Verb,G2840, koinoo ]
to make koinos, "to defile," is translated "unclean" in Hebrews 9:13, AV, where the perfect participle, Passive, is used with the article, hence the RV, "them that have been defiled." See DEFILE, A, No. 1.
[ C-1,Noun,G167, akatharsia ]
akin to A, No. 1, denotes "uncleanness,"
(a) physical, Matthew 23:27 (instances in the papyri speak of tenants keeping houses in good condition);
(b) moral, Romans 1:24; Romans 6:19; 2 Corinthians 12:21; Galatians 5:19; Ephesians 4:19; Ephesians 5:3; Colossians 3:5; 1 Thessalonians 2:3 (suggestive of the fact that sensuality and evil doctrine are frequently associated); 1 Thessalonians 4:7.
Note: In 2 Peter 2:10, AV, miasmos, "a defilement," is rendered "uncleanness;" See DEFILEMENT, B, No. 2.