Quick Definition
ἀθέμιτος, ον Adj illegal, unlawful
Strong's Definition
from 1 (as a negative particle) and a derivative of themis (statute; from the base of 5087); illegal; by implication, flagitious
KJV Usage: abominable, unlawful thing
UBS Dictionary of the Greek New Testament
adjc. | -ον | θέμις (law, right)
13.144 · Be, Become, Exist, Happen · Happen
not allowed, forbidden pertaining to what is not allowed
88.143 · Moral and Ethical Qualities and Related Behavior · Act Lawlessly
disgusting, bad pertaining to being bad and disgusting on the basis of not being allowed
1 Though ἀθέμιτος may be regarded as meaning literally ‘pertaining to what is not allowed’ (13.144), it acquires by association not only the meaning of lawless (a meaning which is possibly applicable to 1PE 4:3) but also disgusting or wanton in connection with idol worship. Such a semantic development is typical of what often happens when meanings shift from an objective to a subjective orientation.
UBS Dictionary of the Greek New Testament © United Bible Societies, licensed CC BY-SA 4.0.
Thayer's Greek Lexicon
ἀ-θέμιτος, -ov, a later form for the ancient and preferable ἀθέμιστος, (θεμιτός, θεμιστός, θεμίζω, θέμις law, right), contrary to law and justice, prohibited by law, illicit, criminal: 1 Pet. iv. 3 [here A. V. abominable]; ἀθέμιτόν ἐστί τινι with inf., Acts x. 28." G-Bc0s, -ov, (Geos), [fr. Pind. down], without God, knowing and worshipping no God, in which sense Ael. ν. h. 2, 31 declares ὅτι μηδεὶς τῶν βαρβάρων ἄθεος ; in classic auth. generally slighting the gods, impious, repudiating the gods recognized by the state, in which sense certain Greek philosophers, the Jews (Joseph. c. Ap. 2, 14, 4), and subsequently Christians were called ἄθεοι by the heathen (Justin, apol. 1, 13, ete.). In Eph. ii. 12 of one who neither knows nor worships the true God; so of the heathen (cf. 1 Th. iv. 5; Gal. iv. 8); Clem. Alex. protr. ii. 23 p. 19 Pott. ἀθέους . . . ot τὸν ὄντως ὄντα θεὸν ἠγνοήκασι, Philo, leg. ad Gai. § 25 αἰγυπτιακὴ ἀθεότης, Hos. ἵν. 15 Symm. οἶκος ἀθεΐας a house in which idols are worshipped, Ignat. ad Trall. 10 ἄθεοι τουτέστιν ἄπιστοι (of the Docetae); [al. understand Eph. 1. 6. passively deserted of God, Vulg. sine Deo; on the various meanings of the word see Mey. (or Ellic.)].
Mounce Concise Greek Dictionary
ἀθέμιτος athemitos 2x
unlawful, criminal, wicked, Acts 10:28; 1 Pet. 4:3*
Abbott-Smith Greek Lexicon
** ἀ-θέμιτος (late form of ἀθέμιστος, LS, MM, VGT, s.v.), -ον
(< θέμις, custom, right), [in LXX: II Mac 6:5 7:1 10:34, III Mac 5:20*;]
of persons, lawless (III Mac 5:20);
of things, lawless, unlawful: Ac 10:28, I Pe 4:3.†
SYN.: v.s. ἄθεσμος.
Moulton & Milligan — Vocabulary of the Greek NT
ἀθέμιτος. This late form is found in P Tor I. 14.” (B.c. 120) als [vc θεαῖς] ἀθέμιτά ἐστιν νεκρὰ σώματα, a passage which ὄθεος 12 seems to support the rendering ‘‘abominable” in 1 Pet 4%, and in consequence perhaps the Gentile destination of the Epistle: see Bigg’s note ad/. Vettius Valens the astrologer (ii/A.D.) tells us that under the influence of Saturn, Mars and Venus some people ἀθεμίτοις μίξεσι καὶ ἀδιαφόροις (“reckless”) ἀνεπιστρεπτοῦσι (p. 43%): the same writer (p. 184°) speaks of men who ἀρνοῦνται τὰ θεῖα καὶ ἑτεροσεβοῦσι ἢ ἀθεμιτοφαγοῦσιν. The word is thus equivalent to nefastus.
Liddell-Scott-Jones — Greek-English Lexicon
ἀθέμιτος (athemitos) — unlawful. ἀθέμ-ιστος or ἀθέμιτος, ον, (the former in Poetry, the latter more correct in Prose) = {ἀθεμίστιος}, [Refs 8th c.BC+]; of the Cyclopes, [Refs 8th c.BC+]; ἀθεμιστότεροι[Refs 5th c.BC+]adverb -ίστως Phaennis cited in [Refs 2nd c.AD+] -ίτως [Refs 2nd c.AD+]
II. of things, unlawful, frequently in neuter, ἀθέμιτα ἔρδειν[NT+5th c.BC+]