The term 'Somersaulting Drinking Vessel' is a crossword solution that can be solved by the word 'TUMBLER' (7 letters). A TUMBLER is a drinking vessel with a flat bottom and straight sides, which allows it to be spun or rolled around. It is commonly used for drinking alcoholic beverages, such as whiskey, and is often made of glass or plastic. The TUMBLER's shape also makes it ideal for somersaulting, which is why it is referred to as a 'somersaulting drinking vessel'.