1(in the Bible) the names of enemies of God’s people. In Ezek. 38-9, Gog is apparently a ruler from the land of Magog, while in Rev. 20:8, Gog and Magog are nations under the dominion of Satan.
2(in medieval legend) opponents of Alexander the Great, living north of the Caucasus.
3two giant statues standing in Guildhall, London, representing either the last two survivors of a race of giants supposed to have inhabited Britain before Roman times, or Gogmagog, chief of the giants, and Corineus, a Roman invader.
Gog and Magog in other Oxford dictionaries
Definition of Gog and Magog in the US English dictionary