the fruit of a tree of the genus citrus (c. aurantium). it is usually round, and consists of pulpy carpels, commonly ten in number, inclosed in a leathery rind, which is easily separable, and is reddish yellow when ripe.-the tree that bears oranges; the orange tree.-the color of an orange; reddish yellow.-of or pertaining to an orange; of the color of an orange; reddish yellow; as, an orange ribbon.