The term 'Drum Signal' is a type of communication used in the military. It is also known as a 'TATTOO, ' which is a six-letter word. A drum signal is a series of beats on a drum that is used to communicate orders or messages to troops. The beats are usually in a specific pattern and can be used to signal the start or end of a battle, or to give instructions to troops. Drum signals were used extensively during the American Revolutionary War and have been used in various other conflicts throughout history.