The term 'whacking tool' can be summarized as a tool used for striking or hitting something. The crossword solution for this term is GAT, which is an acronym for Gun, Automatic, and Tommy. This acronym is used to refer to a type of submachine gun that was developed in the early 20th century. It is a handheld firearm that is capable of firing multiple rounds of ammunition in rapid succession. The GAT was widely used during World War I and II and is still used today by some military forces.