To deliberately buy a stock when its price is falling. When one scales in, one sets a maximum price for that stock. When it falls below that price, one begins buying in small increments until the price stops falling or one reaches one's desired holding. The idea behind scaling in is to lower the average price at which one buys the stock, which can result in a higher return. Scaling in is risky, however, because there is no guarantee that the stock will rise back to its previous level. See also: Average Down.