Lexical Definition

‎ἀκάθαρτος‎ akáthartos (ak-ath'-ar-tos) unclean ^G:A
from ‎Α‎ (as a negative particle) and a presumed derivative of ‎καθαίρω‎ (meaning cleansed)

foul, unclean.

• impure (ceremonially, morally (lewd) or specially, (demonic))

Abbott-Smith

ἀκάθαρτος, -ον (< ἀ- neg., καθαίρω), [in LXX chiefly for טָמֵא;]
unclean, impure;
(a) physically (LS, MM, VGT, s.v.);
(b) ceremonially: Ac 10:14, 28 11:8, I Co 7:14, II Co 6:17, Re 18:2;
(c) morally: Eph 5:5, Re 17:4; c. πνεῦμα, as always in Gosp., Mt 10:1 12:43, Mk 1:23, 26, 27 3:11, 30 5:2, 8, 13 6:7 7:25 9:25, Lk 4:33, 36 6:18 8:29 9:42 11:24, Ac 5:16 8:7, Re 16:13 (cf. Cremer, 320).†

Abbott-Smith References

Liddell-Scott-Jones

ἀκάθαρτος-τος, ον,

(καθαίρω) uncleansed, foul, ἀήρ[Refs 5th c.BC+] of the body, [Refs 5th c.BC+]; of a woman, quae menstrua non habet, [Refs 4th c.BC+]; of ceremonial impurity, [LXX]

__b unpurified, [Refs 5th c.BC+]
__2 morally unclean, impure, [Refs 5th c.BC+]thou beast! [Refs 3rd c.BC+]; ={μανιώδης}, [NT+5th c.BC+]. adverb ἀκαθάρτως, ἔχειν[Refs 5th c.BC+]
__3 ofthings, notpurgedaway, unpurged, [Refs 5th c.BC+]
__3.b unpruned, [Refs 4th c.BC+]
__3.c ceremonially unclean, of food, [LXX+NT]
__3.d not sifted, containing impurities, [Refs 3rd c.BC+]
__II active, not fit for cleansing, [φάρμακα] ἑλκέων ἀκαθαρτότερα[Refs 2nd c.AD+]

_{LSJ Scripture Refs: LXX.Lev.12.2 ☩ LXX.Zech.13.2 ☩ Matt.12.43 ☩ LXX.Lev.5.2 ☩ Acts.10.14}