A flightless bird belonging to a bird group called 'Ratites.' It is second tallest (next to the ostrich.) And is native to Australia. They can be very aggressive if you get close. They are similar to an ostrich in a few ways and different to an ostrich in a few ways.
Me: Hey! I just saw an emu at the zoo.
Friend: Since when do emo kidsgo to the zoo and since when where they called 'emu'
Me: No, idiot, 'emu' is a flightless bird that is a relative to an ostrich. Learn things already!
Australian slang used to describe a person who walks around racecourses picking up discarded tickets. Their actions mimic those of the flightless bird, the Emu (Dromaius novaehollandiae).