The Collaborative International Dictionary of English v.0.48:
oo \o"o\, n. [Hawaiian.] (Zool.) Any of several beautiful birds of the genus Moho, including the extinct Moho nobilis. They are honey-eaters native to the Hawaiian Islands. It yields the brilliant yellow feathers formerly used in making the royal robes. Called also yellow-tufted honeysucker. [1913 Webster]