The term 'PROCESSING UNIT' can be broken down into two words, 'PROCESSING' and 'UNIT'. The word 'PROCESSING' is defined as the action of treating something in order to change or prepare it for a particular purpose. The word 'UNIT' is defined as a single thing or person regarded as a whole. Therefore, the term 'PROCESSING UNIT' can be defined as a single thing or person that is treated in order to change or prepare it for a particular purpose. In the context of a crossword puzzle, the answer to the clue 'Byte' (4 letters) is a UNIT of digital information that typically consists of eight bits. Thus, the term 'PROCESSING UNIT' can refer to a UNIT of digital information that is treated in order to change or prepare it for a particular purpose.