Definition - What does Day Order mean?
Day order is a financial term that means a security should either be sold or bought during the trading hours. If it is not bought or sold during that time, the order is effectively cancelled. It is considered the most usual trading system in securities.
Insuranceopedia explains Day Order
In the stock market, the selling and buying price is volatile and can change over the course a working day. Day orders illustrate this challenge to trading. A day order is issued when selling and buying would be a wise move but this could no longer be the case the following day.