Day Order

What Does Day Order Mean?
Any order to buy or sell a security that automatically expires if not executed on the day the order is placed.

Investopedia explains Day Order
A day order will not be executed if the limit or stop order prices were not met during the day. A way to increase the life of an order is to order securities on a "good until canceled" basis, in which the trade will not expire until it is canceled or until it reaches a maximum time limit set by the brokerage.