【How-to】What does o speak again bright angel mean

JULIET Ay me! 25 ROMEO She speaks: O, speak again, bright angel, for thou art As glorious to this night, being o’er my head As a winged messenger of heaven Unto the white upturned wondering eyes 30 Of mortals that fall back to gaze on him When he bestrides the lazy puffing clouds, And floats upon the bosom of the air.