The term 'Cassowary Cousin' refers to a group of large, flightless birds that are related to the cassowary. This group includes the EMU (3 letters), RHEA (4 letters), emus (4 letters), and RATITE (6 letters). All of these birds are characterized by their lack of a keel on their sternum, which prevents them from flying. They are also known for their long legs and powerful claws, which they use for defense and to help them move around.