Emu \E"mu\, n. [Cf. Pg. ema ostrich, F. ['e]mou, ['e]meu, emu.] (Zo["o]l.) A large Australian bird, of two species ({Dromaius Nov[ae]-Hollandi[ae]} and {D. irroratus}), related to the cassowary and the ostrich. The emu runs swiftly, but is unable to fly. [Written also {emeu} and {emew}.] Note: The name is sometimes erroneously applied, by the Brazilians, to the rhea, or South American ostrich. {Emu wren}. See in the Vocabulary.