A partial fill is a term used in trading to describe an order that has not been completely filled at the desired price, and instead, only a portion of the order has been executed. This means that the trader has received part of the total number of shares or contracts they wanted to buy or sell, but not all of them. A partial fill can happen for various reasons, such as lack of liquidity, price volatility, or delays in processing the order. Traders may have to adjust their strategy or place additional orders to complete their desired trade.