The term FAST BIRD can be broken down into two crossword solutions: EMU (3 letters) and FAST (4 letters). The EMU is a large, flightless bird native to Australia. It is the second-largest living bird by height, after its relative, the ostrich. The EMU is also the fastest bird on the ground, capable of running at speeds of up to 50 km/h. FAST stands for 'Fiber-optic Attenuation and Splicing Technology'. This technology is used in fiber-optic communication systems to reduce signal loss and improve signal quality.