The term OUTBACK FLOCK is composed of two words, the first being 'OUTBACK' and the second being 'FLOCK'. The crossword solution for the first word is EMUS, which is a four-letter word. EMUS are large, flightless birds native to Australia and New Guinea. They are closely related to the ostrich and are the largest living bird in the world by height. OUTBACK is an Australian term used to describe remote, rural areas, so the term OUTBACK FLOCK likely refers to a FLOCK of emus living in a remote area of Australia.