Extended Strong's Greek Lexicon (Abbott-Smith based)
avenging
Usage: ἔκδικος, -ον (δίκη), [in LXX: Wis.12:12, Sir.30:6, 4Ma.15:29 * ;] __1. without law, unjust. __2. exacting penalty from; as subst., an avenger: Rom.13:4; before περί, 1Th.4:6 (in π., a legal representative; Milligan, Th., l.with).† (AS)