The term 'ZOO BIRD' can be summarized by the crossword solution EMU, which is a three-letter word. The EMU is a large, flightless bird native to Australia and the second-largest living bird by height after the ostrich. It is a member of the ratite family, which also includes the ostrich, rhea, and kiwi. Emus are farmed for their meat, oil, and leather, and their feathers are used in traditional Aboriginal ceremonies.