The term 'PART LOUVER' is a combination of two words, 'PART' and 'LOUVER'. A LOUVER is a type of window or door that has horizontal slats, usually made of wood or metal, which are angled to allow air to pass through while still providing some privacy. The word 'PART' in this context refers to the individual slats that make up the LOUVER. Therefore, the term 'PART LOUVER' refers to the individual slats that make up a LOUVER window or door. The crossword solution for this term is 'SLAT', which is a four-letter word meaning a thin, narrow strip of material, such as wood or metal, used to form a LOUVER.