The term 'Supersonic UNIT' can be broken down into two parts: 'Mach' and 'UNIT'. Mach is a UNIT of measurement used to measure the speed of an object relative to the speed of sound. It is named after Ernst Mach, an Austrian physicist and philosopher. The term 'UNIT' refers to a single entity or component of a larger system. In this case, it is referring to a single UNIT of supersonic speed. Therefore, the term 'Supersonic UNIT' can be defined as a single UNIT of speed that is faster than the speed of sound.