Abbott-Smith Manual Greek Lexicon
ἔκδικος (G1558)
2 ** ἔκδικος , -ον ( δίκη ), [in LXX: Wi 12:12 , Si 30:6 , IV Mac 15:29 * ;] without law, unjust . exacting penalty from ; as subst., an avenger : Ro 13:4 ; seq. περί , I Th 4:6 (in π. , a legal representative ; Milligan, Th. , l.c.).†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain