Archaic literary term; a yojijukugo using the mythical golden crow (sun) and jade rabbit (moon). Rarely used in modern Japanese outside of classical or poetic contexts.
See also: 烏兎
「金烏玉兎」は、太陽と月を表す古い四字熟語です。
"Kin'u gyokuto" is an old four-character idiom that represents the sun and moon.