STEP Greek Lexicon: Ἀρμαγεδδών

Ἁρμαγεδών (WH, Ἃρ Μαγεδών; Rec. Ἀρμαγεδδών, prop. = הַר מְגִדּוֹן), cf. LXX, Μαγεδών, 2Ch.35:22, Μαγεδώ, Jdg.1:27; Har-Magedon (AV, Armageddon): Rev.16:16 (see Swete, in l, but also Thayer, see word).†

Ἅρ,

indecl., Rev.16:16, see, Ἁρμαγεδών

Μαγεδών,

Magedon: Rev.16:16 (WH, Ἅρ M. for Ἁρμαγεδών, which see).†

(AS)