(of a couple) to be deeply in love and inseparable, going everywhere together

Literally meaning to fly wing to wing; used to describe a couple who are deeply in love and inseparable.

a pair of legendary birds (also called [[鹣鹣|鶼鶼|jian1 jian1]] or [[蛮蛮|蠻蠻|man2 man2]]) in Chinese mythology, each having only one eye and one wing, that must fly together in pairs

Meaning "in the sky we would be two birds flying wing to wing, and on the earth we would be two trees with branches intertwined"; used to express a wish for a couple to remain together forever, in life and death.