at-the-close order - Investment & Finance Definition
A trade order for a stock, futures, or options contract that is to be executed at the closing price of the security. If the execution can’t occur at the close, then the order is cancelled. In this respect, it is a particular type of all-or-none market order. On futures and options exchanges, there often is a closing period that lasts for approximately ten minutes when at-the-close orders can be executed.