Rainbow means in the bible: A visible sign of God’s covenant with Noah Gen. 1:28; Rev. 4:3; 10:1. Although the rainbow was evidently present before the Flood the symbol of the covenant took on new meaning with Noah. JST Gen.9:17-25 expands on the terms of covenant so that not only will the earth never be again covered by a flood of waters but also the Zion of Enoch and the Lord will again come to live on the earth. Gen.9:11, note c; Gen.9:15 note b; JST Gene 9:21-25 Annexe.
(in Bible Dictionary)