Lexical Definition

‎ἀθέμιτος‎ athémitos (ath-em'-ee-tos) unlawful ^G:A
from ‎Α‎ (as a negative particle) and a derivative of (statute

abominable, unlawful thing.

• from the base of ‎τίθημι‎)
• illegal
• by implication, flagitious

Abbott-Smith

** 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*;]
(a) of persons, lawless (III Mac 5:20);
(b) of things, lawless, unlawful: Ac 10:28, I Pe 4:3.†
SYN.: v.s. ἄθεσμος.

Abbott-Smith References

Liddell-Scott-Jones

ἀθέμιτος-ιστος

or ἀθέμιτοςιτος, 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, ἀθέμιτοςιτα ἔρδειν[ἀθέμιτοςιστον “IG” 14.1389ii29:— ἀ. εἰδωλολατρεῖαι NT.1Pet.4.3: with \_dative\_, αἷς [θεαῖς] ἀ. νεκρὰ σώματα “PTaur.” 1 ii 22 (2nd c.BC).">NT+5th c.BC+]

_{LSJ Scripture Refs: 1Pet.4.3}