The term 'scalp LINE' is a term used in the stock market to refer to the buying and selling of stocks at a certain price. It is the point at which a trader will buy or sell a stock, and it is usually determined by the current market conditions. The four-letter PART of the term is 'LINE', which refers to the LINE of buyers and sellers that form when a stock is traded. This LINE is often referred to as the 'scalp LINE' because traders are trying to make a quick profit by buying and selling stocks quickly.