The term 'Hindmost Part' can be solved by the word 'TAIL', which is a four-letter word. The TAIL is the last part of an animal's body, usually referring to the appendage that extends from the posterior end of the animal. It is used for balance, communication, and other functions. In some animals, such as cats and dogs, the TAIL is used for communication, such as when a dog wags its TAIL to show happiness. In other animals, such as birds, the TAIL is used for balance while flying.